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2488 lines
63 KiB
2488 lines
63 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* linux/ipc/sem.c |
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* Copyright (C) 1992 Krishna Balasubramanian |
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* Copyright (C) 1995 Eric Schenk, Bruno Haible |
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* |
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* /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <[email protected]> |
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* |
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* SMP-threaded, sysctl's added |
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* (c) 1999 Manfred Spraul <[email protected]> |
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* Enforced range limit on SEM_UNDO |
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* (c) 2001 Red Hat Inc |
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* Lockless wakeup |
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* (c) 2003 Manfred Spraul <[email protected]> |
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* (c) 2016 Davidlohr Bueso <[email protected]> |
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* Further wakeup optimizations, documentation |
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* (c) 2010 Manfred Spraul <[email protected]> |
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* |
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* support for audit of ipc object properties and permission changes |
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* Dustin Kirkland <[email protected]> |
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* |
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* namespaces support |
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* OpenVZ, SWsoft Inc. |
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* Pavel Emelianov <[email protected]> |
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* |
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* Implementation notes: (May 2010) |
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* This file implements System V semaphores. |
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* |
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* User space visible behavior: |
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* - FIFO ordering for semop() operations (just FIFO, not starvation |
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* protection) |
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* - multiple semaphore operations that alter the same semaphore in |
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* one semop() are handled. |
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* - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and |
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* SETALL calls. |
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* - two Linux specific semctl() commands: SEM_STAT, SEM_INFO. |
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* - undo adjustments at process exit are limited to 0..SEMVMX. |
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* - namespace are supported. |
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* - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtime by writing |
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* to /proc/sys/kernel/sem. |
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* - statistics about the usage are reported in /proc/sysvipc/sem. |
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* |
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* Internals: |
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* - scalability: |
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* - all global variables are read-mostly. |
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* - semop() calls and semctl(RMID) are synchronized by RCU. |
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* - most operations do write operations (actually: spin_lock calls) to |
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* the per-semaphore array structure. |
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* Thus: Perfect SMP scaling between independent semaphore arrays. |
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* If multiple semaphores in one array are used, then cache line |
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* trashing on the semaphore array spinlock will limit the scaling. |
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* - semncnt and semzcnt are calculated on demand in count_semcnt() |
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* - the task that performs a successful semop() scans the list of all |
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* sleeping tasks and completes any pending operations that can be fulfilled. |
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* Semaphores are actively given to waiting tasks (necessary for FIFO). |
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* (see update_queue()) |
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* - To improve the scalability, the actual wake-up calls are performed after |
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* dropping all locks. (see wake_up_sem_queue_prepare()) |
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* - All work is done by the waker, the woken up task does not have to do |
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* anything - not even acquiring a lock or dropping a refcount. |
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* - A woken up task may not even touch the semaphore array anymore, it may |
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* have been destroyed already by a semctl(RMID). |
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* - UNDO values are stored in an array (one per process and per |
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* semaphore array, lazily allocated). For backwards compatibility, multiple |
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* modes for the UNDO variables are supported (per process, per thread) |
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* (see copy_semundo, CLONE_SYSVSEM) |
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* - There are two lists of the pending operations: a per-array list |
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* and per-semaphore list (stored in the array). This allows to achieve FIFO |
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* ordering without always scanning all pending operations. |
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* The worst-case behavior is nevertheless O(N^2) for N wakeups. |
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*/ |
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|
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#include <linux/compat.h> |
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#include <linux/slab.h> |
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#include <linux/spinlock.h> |
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#include <linux/init.h> |
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#include <linux/proc_fs.h> |
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#include <linux/time.h> |
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#include <linux/security.h> |
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#include <linux/syscalls.h> |
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#include <linux/audit.h> |
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#include <linux/capability.h> |
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#include <linux/seq_file.h> |
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#include <linux/rwsem.h> |
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#include <linux/nsproxy.h> |
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#include <linux/ipc_namespace.h> |
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#include <linux/sched/wake_q.h> |
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#include <linux/nospec.h> |
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#include <linux/rhashtable.h> |
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|
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#include <linux/uaccess.h> |
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#include "util.h" |
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|
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/* One semaphore structure for each semaphore in the system. */ |
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struct sem { |
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int semval; /* current value */ |
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/* |
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* PID of the process that last modified the semaphore. For |
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* Linux, specifically these are: |
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* - semop |
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* - semctl, via SETVAL and SETALL. |
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* - at task exit when performing undo adjustments (see exit_sem). |
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*/ |
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struct pid *sempid; |
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spinlock_t lock; /* spinlock for fine-grained semtimedop */ |
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struct list_head pending_alter; /* pending single-sop operations */ |
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/* that alter the semaphore */ |
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struct list_head pending_const; /* pending single-sop operations */ |
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/* that do not alter the semaphore*/ |
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time64_t sem_otime; /* candidate for sem_otime */ |
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} ____cacheline_aligned_in_smp; |
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|
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/* One sem_array data structure for each set of semaphores in the system. */ |
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struct sem_array { |
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struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */ |
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time64_t sem_ctime; /* create/last semctl() time */ |
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struct list_head pending_alter; /* pending operations */ |
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/* that alter the array */ |
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struct list_head pending_const; /* pending complex operations */ |
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/* that do not alter semvals */ |
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struct list_head list_id; /* undo requests on this array */ |
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int sem_nsems; /* no. of semaphores in array */ |
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int complex_count; /* pending complex operations */ |
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unsigned int use_global_lock;/* >0: global lock required */ |
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|
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struct sem sems[]; |
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} __randomize_layout; |
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|
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/* One queue for each sleeping process in the system. */ |
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struct sem_queue { |
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struct list_head list; /* queue of pending operations */ |
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struct task_struct *sleeper; /* this process */ |
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struct sem_undo *undo; /* undo structure */ |
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struct pid *pid; /* process id of requesting process */ |
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int status; /* completion status of operation */ |
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struct sembuf *sops; /* array of pending operations */ |
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struct sembuf *blocking; /* the operation that blocked */ |
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int nsops; /* number of operations */ |
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bool alter; /* does *sops alter the array? */ |
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bool dupsop; /* sops on more than one sem_num */ |
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}; |
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|
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/* Each task has a list of undo requests. They are executed automatically |
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* when the process exits. |
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*/ |
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struct sem_undo { |
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struct list_head list_proc; /* per-process list: * |
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* all undos from one process |
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* rcu protected */ |
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struct rcu_head rcu; /* rcu struct for sem_undo */ |
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struct sem_undo_list *ulp; /* back ptr to sem_undo_list */ |
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struct list_head list_id; /* per semaphore array list: |
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* all undos for one array */ |
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int semid; /* semaphore set identifier */ |
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short *semadj; /* array of adjustments */ |
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/* one per semaphore */ |
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}; |
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|
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/* sem_undo_list controls shared access to the list of sem_undo structures |
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* that may be shared among all a CLONE_SYSVSEM task group. |
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*/ |
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struct sem_undo_list { |
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refcount_t refcnt; |
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spinlock_t lock; |
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struct list_head list_proc; |
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}; |
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#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) |
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|
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static int newary(struct ipc_namespace *, struct ipc_params *); |
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static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); |
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#ifdef CONFIG_PROC_FS |
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static int sysvipc_sem_proc_show(struct seq_file *s, void *it); |
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#endif |
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|
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#define SEMMSL_FAST 256 /* 512 bytes on stack */ |
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#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ |
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|
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/* |
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* Switching from the mode suitable for simple ops |
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* to the mode for complex ops is costly. Therefore: |
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* use some hysteresis |
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*/ |
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#define USE_GLOBAL_LOCK_HYSTERESIS 10 |
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|
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/* |
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* Locking: |
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* a) global sem_lock() for read/write |
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* sem_undo.id_next, |
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* sem_array.complex_count, |
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* sem_array.pending{_alter,_const}, |
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* sem_array.sem_undo |
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* |
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* b) global or semaphore sem_lock() for read/write: |
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* sem_array.sems[i].pending_{const,alter}: |
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* |
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* c) special: |
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* sem_undo_list.list_proc: |
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* * undo_list->lock for write |
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* * rcu for read |
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* use_global_lock: |
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* * global sem_lock() for write |
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* * either local or global sem_lock() for read. |
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* |
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* Memory ordering: |
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* Most ordering is enforced by using spin_lock() and spin_unlock(). |
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* |
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* Exceptions: |
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* 1) use_global_lock: (SEM_BARRIER_1) |
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* Setting it from non-zero to 0 is a RELEASE, this is ensured by |
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* using smp_store_release(): Immediately after setting it to 0, |
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* a simple op can start. |
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* Testing if it is non-zero is an ACQUIRE, this is ensured by using |
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* smp_load_acquire(). |
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* Setting it from 0 to non-zero must be ordered with regards to |
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* this smp_load_acquire(), this is guaranteed because the smp_load_acquire() |
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* is inside a spin_lock() and after a write from 0 to non-zero a |
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* spin_lock()+spin_unlock() is done. |
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* To prevent the compiler/cpu temporarily writing 0 to use_global_lock, |
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* READ_ONCE()/WRITE_ONCE() is used. |
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* |
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* 2) queue.status: (SEM_BARRIER_2) |
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* Initialization is done while holding sem_lock(), so no further barrier is |
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* required. |
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* Setting it to a result code is a RELEASE, this is ensured by both a |
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* smp_store_release() (for case a) and while holding sem_lock() |
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* (for case b). |
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* The ACQUIRE when reading the result code without holding sem_lock() is |
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* achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep(). |
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* (case a above). |
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* Reading the result code while holding sem_lock() needs no further barriers, |
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* the locks inside sem_lock() enforce ordering (case b above) |
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* |
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* 3) current->state: |
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* current->state is set to TASK_INTERRUPTIBLE while holding sem_lock(). |
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* The wakeup is handled using the wake_q infrastructure. wake_q wakeups may |
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* happen immediately after calling wake_q_add. As wake_q_add_safe() is called |
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* when holding sem_lock(), no further barriers are required. |
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* |
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* See also ipc/mqueue.c for more details on the covered races. |
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*/ |
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|
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#define sc_semmsl sem_ctls[0] |
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#define sc_semmns sem_ctls[1] |
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#define sc_semopm sem_ctls[2] |
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#define sc_semmni sem_ctls[3] |
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|
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void sem_init_ns(struct ipc_namespace *ns) |
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{ |
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ns->sc_semmsl = SEMMSL; |
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ns->sc_semmns = SEMMNS; |
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ns->sc_semopm = SEMOPM; |
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ns->sc_semmni = SEMMNI; |
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ns->used_sems = 0; |
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ipc_init_ids(&ns->ids[IPC_SEM_IDS]); |
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} |
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#ifdef CONFIG_IPC_NS |
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void sem_exit_ns(struct ipc_namespace *ns) |
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{ |
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free_ipcs(ns, &sem_ids(ns), freeary); |
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idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); |
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rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht); |
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} |
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#endif |
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void __init sem_init(void) |
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{ |
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sem_init_ns(&init_ipc_ns); |
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ipc_init_proc_interface("sysvipc/sem", |
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" key semid perms nsems uid gid cuid cgid otime ctime\n", |
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IPC_SEM_IDS, sysvipc_sem_proc_show); |
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} |
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/** |
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* unmerge_queues - unmerge queues, if possible. |
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* @sma: semaphore array |
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* |
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* The function unmerges the wait queues if complex_count is 0. |
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* It must be called prior to dropping the global semaphore array lock. |
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*/ |
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static void unmerge_queues(struct sem_array *sma) |
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{ |
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struct sem_queue *q, *tq; |
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|
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/* complex operations still around? */ |
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if (sma->complex_count) |
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return; |
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/* |
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* We will switch back to simple mode. |
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* Move all pending operation back into the per-semaphore |
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* queues. |
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*/ |
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list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
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struct sem *curr; |
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curr = &sma->sems[q->sops[0].sem_num]; |
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list_add_tail(&q->list, &curr->pending_alter); |
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} |
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INIT_LIST_HEAD(&sma->pending_alter); |
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} |
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/** |
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* merge_queues - merge single semop queues into global queue |
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* @sma: semaphore array |
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* |
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* This function merges all per-semaphore queues into the global queue. |
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* It is necessary to achieve FIFO ordering for the pending single-sop |
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* operations when a multi-semop operation must sleep. |
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* Only the alter operations must be moved, the const operations can stay. |
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*/ |
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static void merge_queues(struct sem_array *sma) |
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{ |
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int i; |
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for (i = 0; i < sma->sem_nsems; i++) { |
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struct sem *sem = &sma->sems[i]; |
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list_splice_init(&sem->pending_alter, &sma->pending_alter); |
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} |
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} |
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static void sem_rcu_free(struct rcu_head *head) |
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{ |
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struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu); |
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struct sem_array *sma = container_of(p, struct sem_array, sem_perm); |
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security_sem_free(&sma->sem_perm); |
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kvfree(sma); |
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} |
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|
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/* |
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* Enter the mode suitable for non-simple operations: |
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* Caller must own sem_perm.lock. |
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*/ |
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static void complexmode_enter(struct sem_array *sma) |
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{ |
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int i; |
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struct sem *sem; |
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if (sma->use_global_lock > 0) { |
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/* |
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* We are already in global lock mode. |
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* Nothing to do, just reset the |
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* counter until we return to simple mode. |
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*/ |
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WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS); |
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return; |
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} |
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WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS); |
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for (i = 0; i < sma->sem_nsems; i++) { |
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sem = &sma->sems[i]; |
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spin_lock(&sem->lock); |
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spin_unlock(&sem->lock); |
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} |
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} |
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|
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/* |
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* Try to leave the mode that disallows simple operations: |
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* Caller must own sem_perm.lock. |
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*/ |
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static void complexmode_tryleave(struct sem_array *sma) |
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{ |
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if (sma->complex_count) { |
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/* Complex ops are sleeping. |
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* We must stay in complex mode |
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*/ |
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return; |
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} |
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if (sma->use_global_lock == 1) { |
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|
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/* See SEM_BARRIER_1 for purpose/pairing */ |
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smp_store_release(&sma->use_global_lock, 0); |
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} else { |
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WRITE_ONCE(sma->use_global_lock, |
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sma->use_global_lock-1); |
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} |
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} |
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#define SEM_GLOBAL_LOCK (-1) |
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/* |
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* If the request contains only one semaphore operation, and there are |
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* no complex transactions pending, lock only the semaphore involved. |
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* Otherwise, lock the entire semaphore array, since we either have |
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* multiple semaphores in our own semops, or we need to look at |
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* semaphores from other pending complex operations. |
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*/ |
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static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, |
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int nsops) |
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{ |
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struct sem *sem; |
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int idx; |
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|
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if (nsops != 1) { |
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/* Complex operation - acquire a full lock */ |
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ipc_lock_object(&sma->sem_perm); |
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|
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/* Prevent parallel simple ops */ |
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complexmode_enter(sma); |
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return SEM_GLOBAL_LOCK; |
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} |
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|
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/* |
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* Only one semaphore affected - try to optimize locking. |
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* Optimized locking is possible if no complex operation |
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* is either enqueued or processed right now. |
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* |
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* Both facts are tracked by use_global_mode. |
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*/ |
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idx = array_index_nospec(sops->sem_num, sma->sem_nsems); |
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sem = &sma->sems[idx]; |
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|
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/* |
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* Initial check for use_global_lock. Just an optimization, |
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* no locking, no memory barrier. |
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*/ |
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if (!READ_ONCE(sma->use_global_lock)) { |
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/* |
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* It appears that no complex operation is around. |
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* Acquire the per-semaphore lock. |
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*/ |
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spin_lock(&sem->lock); |
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|
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/* see SEM_BARRIER_1 for purpose/pairing */ |
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if (!smp_load_acquire(&sma->use_global_lock)) { |
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/* fast path successful! */ |
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return sops->sem_num; |
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} |
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spin_unlock(&sem->lock); |
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} |
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|
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/* slow path: acquire the full lock */ |
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ipc_lock_object(&sma->sem_perm); |
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|
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if (sma->use_global_lock == 0) { |
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/* |
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* The use_global_lock mode ended while we waited for |
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* sma->sem_perm.lock. Thus we must switch to locking |
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* with sem->lock. |
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* Unlike in the fast path, there is no need to recheck |
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* sma->use_global_lock after we have acquired sem->lock: |
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* We own sma->sem_perm.lock, thus use_global_lock cannot |
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* change. |
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*/ |
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spin_lock(&sem->lock); |
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|
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ipc_unlock_object(&sma->sem_perm); |
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return sops->sem_num; |
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} else { |
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/* |
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* Not a false alarm, thus continue to use the global lock |
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* mode. No need for complexmode_enter(), this was done by |
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* the caller that has set use_global_mode to non-zero. |
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*/ |
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return SEM_GLOBAL_LOCK; |
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} |
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} |
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|
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static inline void sem_unlock(struct sem_array *sma, int locknum) |
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{ |
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if (locknum == SEM_GLOBAL_LOCK) { |
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unmerge_queues(sma); |
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complexmode_tryleave(sma); |
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ipc_unlock_object(&sma->sem_perm); |
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} else { |
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struct sem *sem = &sma->sems[locknum]; |
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spin_unlock(&sem->lock); |
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} |
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} |
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|
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/* |
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* sem_lock_(check_) routines are called in the paths where the rwsem |
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* is not held. |
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* |
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* The caller holds the RCU read lock. |
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*/ |
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static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) |
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{ |
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struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id); |
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|
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if (IS_ERR(ipcp)) |
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return ERR_CAST(ipcp); |
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|
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return container_of(ipcp, struct sem_array, sem_perm); |
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} |
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|
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static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns, |
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int id) |
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{ |
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struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id); |
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|
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if (IS_ERR(ipcp)) |
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return ERR_CAST(ipcp); |
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|
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return container_of(ipcp, struct sem_array, sem_perm); |
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} |
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|
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static inline void sem_lock_and_putref(struct sem_array *sma) |
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{ |
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sem_lock(sma, NULL, -1); |
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ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
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} |
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|
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static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) |
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{ |
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ipc_rmid(&sem_ids(ns), &s->sem_perm); |
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} |
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|
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static struct sem_array *sem_alloc(size_t nsems) |
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{ |
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struct sem_array *sma; |
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|
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if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0])) |
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return NULL; |
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|
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sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL_ACCOUNT); |
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if (unlikely(!sma)) |
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return NULL; |
|
|
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return sma; |
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} |
|
|
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/** |
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* newary - Create a new semaphore set |
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* @ns: namespace |
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* @params: ptr to the structure that contains key, semflg and nsems |
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* |
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* Called with sem_ids.rwsem held (as a writer) |
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*/ |
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static int newary(struct ipc_namespace *ns, struct ipc_params *params) |
|
{ |
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int retval; |
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struct sem_array *sma; |
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key_t key = params->key; |
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int nsems = params->u.nsems; |
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int semflg = params->flg; |
|
int i; |
|
|
|
if (!nsems) |
|
return -EINVAL; |
|
if (ns->used_sems + nsems > ns->sc_semmns) |
|
return -ENOSPC; |
|
|
|
sma = sem_alloc(nsems); |
|
if (!sma) |
|
return -ENOMEM; |
|
|
|
sma->sem_perm.mode = (semflg & S_IRWXUGO); |
|
sma->sem_perm.key = key; |
|
|
|
sma->sem_perm.security = NULL; |
|
retval = security_sem_alloc(&sma->sem_perm); |
|
if (retval) { |
|
kvfree(sma); |
|
return retval; |
|
} |
|
|
|
for (i = 0; i < nsems; i++) { |
|
INIT_LIST_HEAD(&sma->sems[i].pending_alter); |
|
INIT_LIST_HEAD(&sma->sems[i].pending_const); |
|
spin_lock_init(&sma->sems[i].lock); |
|
} |
|
|
|
sma->complex_count = 0; |
|
sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; |
|
INIT_LIST_HEAD(&sma->pending_alter); |
|
INIT_LIST_HEAD(&sma->pending_const); |
|
INIT_LIST_HEAD(&sma->list_id); |
|
sma->sem_nsems = nsems; |
|
sma->sem_ctime = ktime_get_real_seconds(); |
|
|
|
/* ipc_addid() locks sma upon success. */ |
|
retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); |
|
if (retval < 0) { |
|
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
|
return retval; |
|
} |
|
ns->used_sems += nsems; |
|
|
|
sem_unlock(sma, -1); |
|
rcu_read_unlock(); |
|
|
|
return sma->sem_perm.id; |
|
} |
|
|
|
|
|
/* |
|
* Called with sem_ids.rwsem and ipcp locked. |
|
*/ |
|
static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params) |
|
{ |
|
struct sem_array *sma; |
|
|
|
sma = container_of(ipcp, struct sem_array, sem_perm); |
|
if (params->u.nsems > sma->sem_nsems) |
|
return -EINVAL; |
|
|
|
return 0; |
|
} |
|
|
|
long ksys_semget(key_t key, int nsems, int semflg) |
|
{ |
|
struct ipc_namespace *ns; |
|
static const struct ipc_ops sem_ops = { |
|
.getnew = newary, |
|
.associate = security_sem_associate, |
|
.more_checks = sem_more_checks, |
|
}; |
|
struct ipc_params sem_params; |
|
|
|
ns = current->nsproxy->ipc_ns; |
|
|
|
if (nsems < 0 || nsems > ns->sc_semmsl) |
|
return -EINVAL; |
|
|
|
sem_params.key = key; |
|
sem_params.flg = semflg; |
|
sem_params.u.nsems = nsems; |
|
|
|
return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); |
|
} |
|
|
|
SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) |
|
{ |
|
return ksys_semget(key, nsems, semflg); |
|
} |
|
|
|
/** |
|
* perform_atomic_semop[_slow] - Attempt to perform semaphore |
|
* operations on a given array. |
|
* @sma: semaphore array |
|
* @q: struct sem_queue that describes the operation |
|
* |
|
* Caller blocking are as follows, based the value |
|
* indicated by the semaphore operation (sem_op): |
|
* |
|
* (1) >0 never blocks. |
|
* (2) 0 (wait-for-zero operation): semval is non-zero. |
|
* (3) <0 attempting to decrement semval to a value smaller than zero. |
|
* |
|
* Returns 0 if the operation was possible. |
|
* Returns 1 if the operation is impossible, the caller must sleep. |
|
* Returns <0 for error codes. |
|
*/ |
|
static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q) |
|
{ |
|
int result, sem_op, nsops; |
|
struct pid *pid; |
|
struct sembuf *sop; |
|
struct sem *curr; |
|
struct sembuf *sops; |
|
struct sem_undo *un; |
|
|
|
sops = q->sops; |
|
nsops = q->nsops; |
|
un = q->undo; |
|
|
|
for (sop = sops; sop < sops + nsops; sop++) { |
|
int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); |
|
curr = &sma->sems[idx]; |
|
sem_op = sop->sem_op; |
|
result = curr->semval; |
|
|
|
if (!sem_op && result) |
|
goto would_block; |
|
|
|
result += sem_op; |
|
if (result < 0) |
|
goto would_block; |
|
if (result > SEMVMX) |
|
goto out_of_range; |
|
|
|
if (sop->sem_flg & SEM_UNDO) { |
|
int undo = un->semadj[sop->sem_num] - sem_op; |
|
/* Exceeding the undo range is an error. */ |
|
if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
|
goto out_of_range; |
|
un->semadj[sop->sem_num] = undo; |
|
} |
|
|
|
curr->semval = result; |
|
} |
|
|
|
sop--; |
|
pid = q->pid; |
|
while (sop >= sops) { |
|
ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid); |
|
sop--; |
|
} |
|
|
|
return 0; |
|
|
|
out_of_range: |
|
result = -ERANGE; |
|
goto undo; |
|
|
|
would_block: |
|
q->blocking = sop; |
|
|
|
if (sop->sem_flg & IPC_NOWAIT) |
|
result = -EAGAIN; |
|
else |
|
result = 1; |
|
|
|
undo: |
|
sop--; |
|
while (sop >= sops) { |
|
sem_op = sop->sem_op; |
|
sma->sems[sop->sem_num].semval -= sem_op; |
|
if (sop->sem_flg & SEM_UNDO) |
|
un->semadj[sop->sem_num] += sem_op; |
|
sop--; |
|
} |
|
|
|
return result; |
|
} |
|
|
|
static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q) |
|
{ |
|
int result, sem_op, nsops; |
|
struct sembuf *sop; |
|
struct sem *curr; |
|
struct sembuf *sops; |
|
struct sem_undo *un; |
|
|
|
sops = q->sops; |
|
nsops = q->nsops; |
|
un = q->undo; |
|
|
|
if (unlikely(q->dupsop)) |
|
return perform_atomic_semop_slow(sma, q); |
|
|
|
/* |
|
* We scan the semaphore set twice, first to ensure that the entire |
|
* operation can succeed, therefore avoiding any pointless writes |
|
* to shared memory and having to undo such changes in order to block |
|
* until the operations can go through. |
|
*/ |
|
for (sop = sops; sop < sops + nsops; sop++) { |
|
int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); |
|
|
|
curr = &sma->sems[idx]; |
|
sem_op = sop->sem_op; |
|
result = curr->semval; |
|
|
|
if (!sem_op && result) |
|
goto would_block; /* wait-for-zero */ |
|
|
|
result += sem_op; |
|
if (result < 0) |
|
goto would_block; |
|
|
|
if (result > SEMVMX) |
|
return -ERANGE; |
|
|
|
if (sop->sem_flg & SEM_UNDO) { |
|
int undo = un->semadj[sop->sem_num] - sem_op; |
|
|
|
/* Exceeding the undo range is an error. */ |
|
if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
|
return -ERANGE; |
|
} |
|
} |
|
|
|
for (sop = sops; sop < sops + nsops; sop++) { |
|
curr = &sma->sems[sop->sem_num]; |
|
sem_op = sop->sem_op; |
|
result = curr->semval; |
|
|
|
if (sop->sem_flg & SEM_UNDO) { |
|
int undo = un->semadj[sop->sem_num] - sem_op; |
|
|
|
un->semadj[sop->sem_num] = undo; |
|
} |
|
curr->semval += sem_op; |
|
ipc_update_pid(&curr->sempid, q->pid); |
|
} |
|
|
|
return 0; |
|
|
|
would_block: |
|
q->blocking = sop; |
|
return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1; |
|
} |
|
|
|
static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error, |
|
struct wake_q_head *wake_q) |
|
{ |
|
struct task_struct *sleeper; |
|
|
|
sleeper = get_task_struct(q->sleeper); |
|
|
|
/* see SEM_BARRIER_2 for purpose/pairing */ |
|
smp_store_release(&q->status, error); |
|
|
|
wake_q_add_safe(wake_q, sleeper); |
|
} |
|
|
|
static void unlink_queue(struct sem_array *sma, struct sem_queue *q) |
|
{ |
|
list_del(&q->list); |
|
if (q->nsops > 1) |
|
sma->complex_count--; |
|
} |
|
|
|
/** check_restart(sma, q) |
|
* @sma: semaphore array |
|
* @q: the operation that just completed |
|
* |
|
* update_queue is O(N^2) when it restarts scanning the whole queue of |
|
* waiting operations. Therefore this function checks if the restart is |
|
* really necessary. It is called after a previously waiting operation |
|
* modified the array. |
|
* Note that wait-for-zero operations are handled without restart. |
|
*/ |
|
static inline int check_restart(struct sem_array *sma, struct sem_queue *q) |
|
{ |
|
/* pending complex alter operations are too difficult to analyse */ |
|
if (!list_empty(&sma->pending_alter)) |
|
return 1; |
|
|
|
/* we were a sleeping complex operation. Too difficult */ |
|
if (q->nsops > 1) |
|
return 1; |
|
|
|
/* It is impossible that someone waits for the new value: |
|
* - complex operations always restart. |
|
* - wait-for-zero are handled separately. |
|
* - q is a previously sleeping simple operation that |
|
* altered the array. It must be a decrement, because |
|
* simple increments never sleep. |
|
* - If there are older (higher priority) decrements |
|
* in the queue, then they have observed the original |
|
* semval value and couldn't proceed. The operation |
|
* decremented to value - thus they won't proceed either. |
|
*/ |
|
return 0; |
|
} |
|
|
|
/** |
|
* wake_const_ops - wake up non-alter tasks |
|
* @sma: semaphore array. |
|
* @semnum: semaphore that was modified. |
|
* @wake_q: lockless wake-queue head. |
|
* |
|
* wake_const_ops must be called after a semaphore in a semaphore array |
|
* was set to 0. If complex const operations are pending, wake_const_ops must |
|
* be called with semnum = -1, as well as with the number of each modified |
|
* semaphore. |
|
* The tasks that must be woken up are added to @wake_q. The return code |
|
* is stored in q->pid. |
|
* The function returns 1 if at least one operation was completed successfully. |
|
*/ |
|
static int wake_const_ops(struct sem_array *sma, int semnum, |
|
struct wake_q_head *wake_q) |
|
{ |
|
struct sem_queue *q, *tmp; |
|
struct list_head *pending_list; |
|
int semop_completed = 0; |
|
|
|
if (semnum == -1) |
|
pending_list = &sma->pending_const; |
|
else |
|
pending_list = &sma->sems[semnum].pending_const; |
|
|
|
list_for_each_entry_safe(q, tmp, pending_list, list) { |
|
int error = perform_atomic_semop(sma, q); |
|
|
|
if (error > 0) |
|
continue; |
|
/* operation completed, remove from queue & wakeup */ |
|
unlink_queue(sma, q); |
|
|
|
wake_up_sem_queue_prepare(q, error, wake_q); |
|
if (error == 0) |
|
semop_completed = 1; |
|
} |
|
|
|
return semop_completed; |
|
} |
|
|
|
/** |
|
* do_smart_wakeup_zero - wakeup all wait for zero tasks |
|
* @sma: semaphore array |
|
* @sops: operations that were performed |
|
* @nsops: number of operations |
|
* @wake_q: lockless wake-queue head |
|
* |
|
* Checks all required queue for wait-for-zero operations, based |
|
* on the actual changes that were performed on the semaphore array. |
|
* The function returns 1 if at least one operation was completed successfully. |
|
*/ |
|
static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops, |
|
int nsops, struct wake_q_head *wake_q) |
|
{ |
|
int i; |
|
int semop_completed = 0; |
|
int got_zero = 0; |
|
|
|
/* first: the per-semaphore queues, if known */ |
|
if (sops) { |
|
for (i = 0; i < nsops; i++) { |
|
int num = sops[i].sem_num; |
|
|
|
if (sma->sems[num].semval == 0) { |
|
got_zero = 1; |
|
semop_completed |= wake_const_ops(sma, num, wake_q); |
|
} |
|
} |
|
} else { |
|
/* |
|
* No sops means modified semaphores not known. |
|
* Assume all were changed. |
|
*/ |
|
for (i = 0; i < sma->sem_nsems; i++) { |
|
if (sma->sems[i].semval == 0) { |
|
got_zero = 1; |
|
semop_completed |= wake_const_ops(sma, i, wake_q); |
|
} |
|
} |
|
} |
|
/* |
|
* If one of the modified semaphores got 0, |
|
* then check the global queue, too. |
|
*/ |
|
if (got_zero) |
|
semop_completed |= wake_const_ops(sma, -1, wake_q); |
|
|
|
return semop_completed; |
|
} |
|
|
|
|
|
/** |
|
* update_queue - look for tasks that can be completed. |
|
* @sma: semaphore array. |
|
* @semnum: semaphore that was modified. |
|
* @wake_q: lockless wake-queue head. |
|
* |
|
* update_queue must be called after a semaphore in a semaphore array |
|
* was modified. If multiple semaphores were modified, update_queue must |
|
* be called with semnum = -1, as well as with the number of each modified |
|
* semaphore. |
|
* The tasks that must be woken up are added to @wake_q. The return code |
|
* is stored in q->pid. |
|
* The function internally checks if const operations can now succeed. |
|
* |
|
* The function return 1 if at least one semop was completed successfully. |
|
*/ |
|
static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q) |
|
{ |
|
struct sem_queue *q, *tmp; |
|
struct list_head *pending_list; |
|
int semop_completed = 0; |
|
|
|
if (semnum == -1) |
|
pending_list = &sma->pending_alter; |
|
else |
|
pending_list = &sma->sems[semnum].pending_alter; |
|
|
|
again: |
|
list_for_each_entry_safe(q, tmp, pending_list, list) { |
|
int error, restart; |
|
|
|
/* If we are scanning the single sop, per-semaphore list of |
|
* one semaphore and that semaphore is 0, then it is not |
|
* necessary to scan further: simple increments |
|
* that affect only one entry succeed immediately and cannot |
|
* be in the per semaphore pending queue, and decrements |
|
* cannot be successful if the value is already 0. |
|
*/ |
|
if (semnum != -1 && sma->sems[semnum].semval == 0) |
|
break; |
|
|
|
error = perform_atomic_semop(sma, q); |
|
|
|
/* Does q->sleeper still need to sleep? */ |
|
if (error > 0) |
|
continue; |
|
|
|
unlink_queue(sma, q); |
|
|
|
if (error) { |
|
restart = 0; |
|
} else { |
|
semop_completed = 1; |
|
do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q); |
|
restart = check_restart(sma, q); |
|
} |
|
|
|
wake_up_sem_queue_prepare(q, error, wake_q); |
|
if (restart) |
|
goto again; |
|
} |
|
return semop_completed; |
|
} |
|
|
|
/** |
|
* set_semotime - set sem_otime |
|
* @sma: semaphore array |
|
* @sops: operations that modified the array, may be NULL |
|
* |
|
* sem_otime is replicated to avoid cache line trashing. |
|
* This function sets one instance to the current time. |
|
*/ |
|
static void set_semotime(struct sem_array *sma, struct sembuf *sops) |
|
{ |
|
if (sops == NULL) { |
|
sma->sems[0].sem_otime = ktime_get_real_seconds(); |
|
} else { |
|
sma->sems[sops[0].sem_num].sem_otime = |
|
ktime_get_real_seconds(); |
|
} |
|
} |
|
|
|
/** |
|
* do_smart_update - optimized update_queue |
|
* @sma: semaphore array |
|
* @sops: operations that were performed |
|
* @nsops: number of operations |
|
* @otime: force setting otime |
|
* @wake_q: lockless wake-queue head |
|
* |
|
* do_smart_update() does the required calls to update_queue and wakeup_zero, |
|
* based on the actual changes that were performed on the semaphore array. |
|
* Note that the function does not do the actual wake-up: the caller is |
|
* responsible for calling wake_up_q(). |
|
* It is safe to perform this call after dropping all locks. |
|
*/ |
|
static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, |
|
int otime, struct wake_q_head *wake_q) |
|
{ |
|
int i; |
|
|
|
otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q); |
|
|
|
if (!list_empty(&sma->pending_alter)) { |
|
/* semaphore array uses the global queue - just process it. */ |
|
otime |= update_queue(sma, -1, wake_q); |
|
} else { |
|
if (!sops) { |
|
/* |
|
* No sops, thus the modified semaphores are not |
|
* known. Check all. |
|
*/ |
|
for (i = 0; i < sma->sem_nsems; i++) |
|
otime |= update_queue(sma, i, wake_q); |
|
} else { |
|
/* |
|
* Check the semaphores that were increased: |
|
* - No complex ops, thus all sleeping ops are |
|
* decrease. |
|
* - if we decreased the value, then any sleeping |
|
* semaphore ops won't be able to run: If the |
|
* previous value was too small, then the new |
|
* value will be too small, too. |
|
*/ |
|
for (i = 0; i < nsops; i++) { |
|
if (sops[i].sem_op > 0) { |
|
otime |= update_queue(sma, |
|
sops[i].sem_num, wake_q); |
|
} |
|
} |
|
} |
|
} |
|
if (otime) |
|
set_semotime(sma, sops); |
|
} |
|
|
|
/* |
|
* check_qop: Test if a queued operation sleeps on the semaphore semnum |
|
*/ |
|
static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, |
|
bool count_zero) |
|
{ |
|
struct sembuf *sop = q->blocking; |
|
|
|
/* |
|
* Linux always (since 0.99.10) reported a task as sleeping on all |
|
* semaphores. This violates SUS, therefore it was changed to the |
|
* standard compliant behavior. |
|
* Give the administrators a chance to notice that an application |
|
* might misbehave because it relies on the Linux behavior. |
|
*/ |
|
pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n" |
|
"The task %s (%d) triggered the difference, watch for misbehavior.\n", |
|
current->comm, task_pid_nr(current)); |
|
|
|
if (sop->sem_num != semnum) |
|
return 0; |
|
|
|
if (count_zero && sop->sem_op == 0) |
|
return 1; |
|
if (!count_zero && sop->sem_op < 0) |
|
return 1; |
|
|
|
return 0; |
|
} |
|
|
|
/* The following counts are associated to each semaphore: |
|
* semncnt number of tasks waiting on semval being nonzero |
|
* semzcnt number of tasks waiting on semval being zero |
|
* |
|
* Per definition, a task waits only on the semaphore of the first semop |
|
* that cannot proceed, even if additional operation would block, too. |
|
*/ |
|
static int count_semcnt(struct sem_array *sma, ushort semnum, |
|
bool count_zero) |
|
{ |
|
struct list_head *l; |
|
struct sem_queue *q; |
|
int semcnt; |
|
|
|
semcnt = 0; |
|
/* First: check the simple operations. They are easy to evaluate */ |
|
if (count_zero) |
|
l = &sma->sems[semnum].pending_const; |
|
else |
|
l = &sma->sems[semnum].pending_alter; |
|
|
|
list_for_each_entry(q, l, list) { |
|
/* all task on a per-semaphore list sleep on exactly |
|
* that semaphore |
|
*/ |
|
semcnt++; |
|
} |
|
|
|
/* Then: check the complex operations. */ |
|
list_for_each_entry(q, &sma->pending_alter, list) { |
|
semcnt += check_qop(sma, semnum, q, count_zero); |
|
} |
|
if (count_zero) { |
|
list_for_each_entry(q, &sma->pending_const, list) { |
|
semcnt += check_qop(sma, semnum, q, count_zero); |
|
} |
|
} |
|
return semcnt; |
|
} |
|
|
|
/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked |
|
* as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem |
|
* remains locked on exit. |
|
*/ |
|
static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) |
|
{ |
|
struct sem_undo *un, *tu; |
|
struct sem_queue *q, *tq; |
|
struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
|
int i; |
|
DEFINE_WAKE_Q(wake_q); |
|
|
|
/* Free the existing undo structures for this semaphore set. */ |
|
ipc_assert_locked_object(&sma->sem_perm); |
|
list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { |
|
list_del(&un->list_id); |
|
spin_lock(&un->ulp->lock); |
|
un->semid = -1; |
|
list_del_rcu(&un->list_proc); |
|
spin_unlock(&un->ulp->lock); |
|
kvfree_rcu(un, rcu); |
|
} |
|
|
|
/* Wake up all pending processes and let them fail with EIDRM. */ |
|
list_for_each_entry_safe(q, tq, &sma->pending_const, list) { |
|
unlink_queue(sma, q); |
|
wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
|
} |
|
|
|
list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
|
unlink_queue(sma, q); |
|
wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
|
} |
|
for (i = 0; i < sma->sem_nsems; i++) { |
|
struct sem *sem = &sma->sems[i]; |
|
list_for_each_entry_safe(q, tq, &sem->pending_const, list) { |
|
unlink_queue(sma, q); |
|
wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
|
} |
|
list_for_each_entry_safe(q, tq, &sem->pending_alter, list) { |
|
unlink_queue(sma, q); |
|
wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
|
} |
|
ipc_update_pid(&sem->sempid, NULL); |
|
} |
|
|
|
/* Remove the semaphore set from the IDR */ |
|
sem_rmid(ns, sma); |
|
sem_unlock(sma, -1); |
|
rcu_read_unlock(); |
|
|
|
wake_up_q(&wake_q); |
|
ns->used_sems -= sma->sem_nsems; |
|
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
|
} |
|
|
|
static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) |
|
{ |
|
switch (version) { |
|
case IPC_64: |
|
return copy_to_user(buf, in, sizeof(*in)); |
|
case IPC_OLD: |
|
{ |
|
struct semid_ds out; |
|
|
|
memset(&out, 0, sizeof(out)); |
|
|
|
ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); |
|
|
|
out.sem_otime = in->sem_otime; |
|
out.sem_ctime = in->sem_ctime; |
|
out.sem_nsems = in->sem_nsems; |
|
|
|
return copy_to_user(buf, &out, sizeof(out)); |
|
} |
|
default: |
|
return -EINVAL; |
|
} |
|
} |
|
|
|
static time64_t get_semotime(struct sem_array *sma) |
|
{ |
|
int i; |
|
time64_t res; |
|
|
|
res = sma->sems[0].sem_otime; |
|
for (i = 1; i < sma->sem_nsems; i++) { |
|
time64_t to = sma->sems[i].sem_otime; |
|
|
|
if (to > res) |
|
res = to; |
|
} |
|
return res; |
|
} |
|
|
|
static int semctl_stat(struct ipc_namespace *ns, int semid, |
|
int cmd, struct semid64_ds *semid64) |
|
{ |
|
struct sem_array *sma; |
|
time64_t semotime; |
|
int err; |
|
|
|
memset(semid64, 0, sizeof(*semid64)); |
|
|
|
rcu_read_lock(); |
|
if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) { |
|
sma = sem_obtain_object(ns, semid); |
|
if (IS_ERR(sma)) { |
|
err = PTR_ERR(sma); |
|
goto out_unlock; |
|
} |
|
} else { /* IPC_STAT */ |
|
sma = sem_obtain_object_check(ns, semid); |
|
if (IS_ERR(sma)) { |
|
err = PTR_ERR(sma); |
|
goto out_unlock; |
|
} |
|
} |
|
|
|
/* see comment for SHM_STAT_ANY */ |
|
if (cmd == SEM_STAT_ANY) |
|
audit_ipc_obj(&sma->sem_perm); |
|
else { |
|
err = -EACCES; |
|
if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) |
|
goto out_unlock; |
|
} |
|
|
|
err = security_sem_semctl(&sma->sem_perm, cmd); |
|
if (err) |
|
goto out_unlock; |
|
|
|
ipc_lock_object(&sma->sem_perm); |
|
|
|
if (!ipc_valid_object(&sma->sem_perm)) { |
|
ipc_unlock_object(&sma->sem_perm); |
|
err = -EIDRM; |
|
goto out_unlock; |
|
} |
|
|
|
kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm); |
|
semotime = get_semotime(sma); |
|
semid64->sem_otime = semotime; |
|
semid64->sem_ctime = sma->sem_ctime; |
|
#ifndef CONFIG_64BIT |
|
semid64->sem_otime_high = semotime >> 32; |
|
semid64->sem_ctime_high = sma->sem_ctime >> 32; |
|
#endif |
|
semid64->sem_nsems = sma->sem_nsems; |
|
|
|
if (cmd == IPC_STAT) { |
|
/* |
|
* As defined in SUS: |
|
* Return 0 on success |
|
*/ |
|
err = 0; |
|
} else { |
|
/* |
|
* SEM_STAT and SEM_STAT_ANY (both Linux specific) |
|
* Return the full id, including the sequence number |
|
*/ |
|
err = sma->sem_perm.id; |
|
} |
|
ipc_unlock_object(&sma->sem_perm); |
|
out_unlock: |
|
rcu_read_unlock(); |
|
return err; |
|
} |
|
|
|
static int semctl_info(struct ipc_namespace *ns, int semid, |
|
int cmd, void __user *p) |
|
{ |
|
struct seminfo seminfo; |
|
int max_idx; |
|
int err; |
|
|
|
err = security_sem_semctl(NULL, cmd); |
|
if (err) |
|
return err; |
|
|
|
memset(&seminfo, 0, sizeof(seminfo)); |
|
seminfo.semmni = ns->sc_semmni; |
|
seminfo.semmns = ns->sc_semmns; |
|
seminfo.semmsl = ns->sc_semmsl; |
|
seminfo.semopm = ns->sc_semopm; |
|
seminfo.semvmx = SEMVMX; |
|
seminfo.semmnu = SEMMNU; |
|
seminfo.semmap = SEMMAP; |
|
seminfo.semume = SEMUME; |
|
down_read(&sem_ids(ns).rwsem); |
|
if (cmd == SEM_INFO) { |
|
seminfo.semusz = sem_ids(ns).in_use; |
|
seminfo.semaem = ns->used_sems; |
|
} else { |
|
seminfo.semusz = SEMUSZ; |
|
seminfo.semaem = SEMAEM; |
|
} |
|
max_idx = ipc_get_maxidx(&sem_ids(ns)); |
|
up_read(&sem_ids(ns).rwsem); |
|
if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) |
|
return -EFAULT; |
|
return (max_idx < 0) ? 0 : max_idx; |
|
} |
|
|
|
static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, |
|
int val) |
|
{ |
|
struct sem_undo *un; |
|
struct sem_array *sma; |
|
struct sem *curr; |
|
int err; |
|
DEFINE_WAKE_Q(wake_q); |
|
|
|
if (val > SEMVMX || val < 0) |
|
return -ERANGE; |
|
|
|
rcu_read_lock(); |
|
sma = sem_obtain_object_check(ns, semid); |
|
if (IS_ERR(sma)) { |
|
rcu_read_unlock(); |
|
return PTR_ERR(sma); |
|
} |
|
|
|
if (semnum < 0 || semnum >= sma->sem_nsems) { |
|
rcu_read_unlock(); |
|
return -EINVAL; |
|
} |
|
|
|
|
|
if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) { |
|
rcu_read_unlock(); |
|
return -EACCES; |
|
} |
|
|
|
err = security_sem_semctl(&sma->sem_perm, SETVAL); |
|
if (err) { |
|
rcu_read_unlock(); |
|
return -EACCES; |
|
} |
|
|
|
sem_lock(sma, NULL, -1); |
|
|
|
if (!ipc_valid_object(&sma->sem_perm)) { |
|
sem_unlock(sma, -1); |
|
rcu_read_unlock(); |
|
return -EIDRM; |
|
} |
|
|
|
semnum = array_index_nospec(semnum, sma->sem_nsems); |
|
curr = &sma->sems[semnum]; |
|
|
|
ipc_assert_locked_object(&sma->sem_perm); |
|
list_for_each_entry(un, &sma->list_id, list_id) |
|
un->semadj[semnum] = 0; |
|
|
|
curr->semval = val; |
|
ipc_update_pid(&curr->sempid, task_tgid(current)); |
|
sma->sem_ctime = ktime_get_real_seconds(); |
|
/* maybe some queued-up processes were waiting for this */ |
|
do_smart_update(sma, NULL, 0, 0, &wake_q); |
|
sem_unlock(sma, -1); |
|
rcu_read_unlock(); |
|
wake_up_q(&wake_q); |
|
return 0; |
|
} |
|
|
|
static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, |
|
int cmd, void __user *p) |
|
{ |
|
struct sem_array *sma; |
|
struct sem *curr; |
|
int err, nsems; |
|
ushort fast_sem_io[SEMMSL_FAST]; |
|
ushort *sem_io = fast_sem_io; |
|
DEFINE_WAKE_Q(wake_q); |
|
|
|
rcu_read_lock(); |
|
sma = sem_obtain_object_check(ns, semid); |
|
if (IS_ERR(sma)) { |
|
rcu_read_unlock(); |
|
return PTR_ERR(sma); |
|
} |
|
|
|
nsems = sma->sem_nsems; |
|
|
|
err = -EACCES; |
|
if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO)) |
|
goto out_rcu_wakeup; |
|
|
|
err = security_sem_semctl(&sma->sem_perm, cmd); |
|
if (err) |
|
goto out_rcu_wakeup; |
|
|
|
err = -EACCES; |
|
switch (cmd) { |
|
case GETALL: |
|
{ |
|
ushort __user *array = p; |
|
int i; |
|
|
|
sem_lock(sma, NULL, -1); |
|
if (!ipc_valid_object(&sma->sem_perm)) { |
|
err = -EIDRM; |
|
goto out_unlock; |
|
} |
|
if (nsems > SEMMSL_FAST) { |
|
if (!ipc_rcu_getref(&sma->sem_perm)) { |
|
err = -EIDRM; |
|
goto out_unlock; |
|
} |
|
sem_unlock(sma, -1); |
|
rcu_read_unlock(); |
|
sem_io = kvmalloc_array(nsems, sizeof(ushort), |
|
GFP_KERNEL); |
|
if (sem_io == NULL) { |
|
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
|
return -ENOMEM; |
|
} |
|
|
|
rcu_read_lock(); |
|
sem_lock_and_putref(sma); |
|
if (!ipc_valid_object(&sma->sem_perm)) { |
|
err = -EIDRM; |
|
goto out_unlock; |
|
} |
|
} |
|
for (i = 0; i < sma->sem_nsems; i++) |
|
sem_io[i] = sma->sems[i].semval; |
|
sem_unlock(sma, -1); |
|
rcu_read_unlock(); |
|
err = 0; |
|
if (copy_to_user(array, sem_io, nsems*sizeof(ushort))) |
|
err = -EFAULT; |
|
goto out_free; |
|
} |
|
case SETALL: |
|
{ |
|
int i; |
|
struct sem_undo *un; |
|
|
|
if (!ipc_rcu_getref(&sma->sem_perm)) { |
|
err = -EIDRM; |
|
goto out_rcu_wakeup; |
|
} |
|
rcu_read_unlock(); |
|
|
|
if (nsems > SEMMSL_FAST) { |
|
sem_io = kvmalloc_array(nsems, sizeof(ushort), |
|
GFP_KERNEL); |
|
if (sem_io == NULL) { |
|
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
|
return -ENOMEM; |
|
} |
|
} |
|
|
|
if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) { |
|
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
|
err = -EFAULT; |
|
goto out_free; |
|
} |
|
|
|
for (i = 0; i < nsems; i++) { |
|
if (sem_io[i] > SEMVMX) { |
|
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
|
err = -ERANGE; |
|
goto out_free; |
|
} |
|
} |
|
rcu_read_lock(); |
|
sem_lock_and_putref(sma); |
|
if (!ipc_valid_object(&sma->sem_perm)) { |
|
err = -EIDRM; |
|
goto out_unlock; |
|
} |
|
|
|
for (i = 0; i < nsems; i++) { |
|
sma->sems[i].semval = sem_io[i]; |
|
ipc_update_pid(&sma->sems[i].sempid, task_tgid(current)); |
|
} |
|
|
|
ipc_assert_locked_object(&sma->sem_perm); |
|
list_for_each_entry(un, &sma->list_id, list_id) { |
|
for (i = 0; i < nsems; i++) |
|
un->semadj[i] = 0; |
|
} |
|
sma->sem_ctime = ktime_get_real_seconds(); |
|
/* maybe some queued-up processes were waiting for this */ |
|
do_smart_update(sma, NULL, 0, 0, &wake_q); |
|
err = 0; |
|
goto out_unlock; |
|
} |
|
/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */ |
|
} |
|
err = -EINVAL; |
|
if (semnum < 0 || semnum >= nsems) |
|
goto out_rcu_wakeup; |
|
|
|
sem_lock(sma, NULL, -1); |
|
if (!ipc_valid_object(&sma->sem_perm)) { |
|
err = -EIDRM; |
|
goto out_unlock; |
|
} |
|
|
|
semnum = array_index_nospec(semnum, nsems); |
|
curr = &sma->sems[semnum]; |
|
|
|
switch (cmd) { |
|
case GETVAL: |
|
err = curr->semval; |
|
goto out_unlock; |
|
case GETPID: |
|
err = pid_vnr(curr->sempid); |
|
goto out_unlock; |
|
case GETNCNT: |
|
err = count_semcnt(sma, semnum, 0); |
|
goto out_unlock; |
|
case GETZCNT: |
|
err = count_semcnt(sma, semnum, 1); |
|
goto out_unlock; |
|
} |
|
|
|
out_unlock: |
|
sem_unlock(sma, -1); |
|
out_rcu_wakeup: |
|
rcu_read_unlock(); |
|
wake_up_q(&wake_q); |
|
out_free: |
|
if (sem_io != fast_sem_io) |
|
kvfree(sem_io); |
|
return err; |
|
} |
|
|
|
static inline unsigned long |
|
copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) |
|
{ |
|
switch (version) { |
|
case IPC_64: |
|
if (copy_from_user(out, buf, sizeof(*out))) |
|
return -EFAULT; |
|
return 0; |
|
case IPC_OLD: |
|
{ |
|
struct semid_ds tbuf_old; |
|
|
|
if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) |
|
return -EFAULT; |
|
|
|
out->sem_perm.uid = tbuf_old.sem_perm.uid; |
|
out->sem_perm.gid = tbuf_old.sem_perm.gid; |
|
out->sem_perm.mode = tbuf_old.sem_perm.mode; |
|
|
|
return 0; |
|
} |
|
default: |
|
return -EINVAL; |
|
} |
|
} |
|
|
|
/* |
|
* This function handles some semctl commands which require the rwsem |
|
* to be held in write mode. |
|
* NOTE: no locks must be held, the rwsem is taken inside this function. |
|
*/ |
|
static int semctl_down(struct ipc_namespace *ns, int semid, |
|
int cmd, struct semid64_ds *semid64) |
|
{ |
|
struct sem_array *sma; |
|
int err; |
|
struct kern_ipc_perm *ipcp; |
|
|
|
down_write(&sem_ids(ns).rwsem); |
|
rcu_read_lock(); |
|
|
|
ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd, |
|
&semid64->sem_perm, 0); |
|
if (IS_ERR(ipcp)) { |
|
err = PTR_ERR(ipcp); |
|
goto out_unlock1; |
|
} |
|
|
|
sma = container_of(ipcp, struct sem_array, sem_perm); |
|
|
|
err = security_sem_semctl(&sma->sem_perm, cmd); |
|
if (err) |
|
goto out_unlock1; |
|
|
|
switch (cmd) { |
|
case IPC_RMID: |
|
sem_lock(sma, NULL, -1); |
|
/* freeary unlocks the ipc object and rcu */ |
|
freeary(ns, ipcp); |
|
goto out_up; |
|
case IPC_SET: |
|
sem_lock(sma, NULL, -1); |
|
err = ipc_update_perm(&semid64->sem_perm, ipcp); |
|
if (err) |
|
goto out_unlock0; |
|
sma->sem_ctime = ktime_get_real_seconds(); |
|
break; |
|
default: |
|
err = -EINVAL; |
|
goto out_unlock1; |
|
} |
|
|
|
out_unlock0: |
|
sem_unlock(sma, -1); |
|
out_unlock1: |
|
rcu_read_unlock(); |
|
out_up: |
|
up_write(&sem_ids(ns).rwsem); |
|
return err; |
|
} |
|
|
|
static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version) |
|
{ |
|
struct ipc_namespace *ns; |
|
void __user *p = (void __user *)arg; |
|
struct semid64_ds semid64; |
|
int err; |
|
|
|
if (semid < 0) |
|
return -EINVAL; |
|
|
|
ns = current->nsproxy->ipc_ns; |
|
|
|
switch (cmd) { |
|
case IPC_INFO: |
|
case SEM_INFO: |
|
return semctl_info(ns, semid, cmd, p); |
|
case IPC_STAT: |
|
case SEM_STAT: |
|
case SEM_STAT_ANY: |
|
err = semctl_stat(ns, semid, cmd, &semid64); |
|
if (err < 0) |
|
return err; |
|
if (copy_semid_to_user(p, &semid64, version)) |
|
err = -EFAULT; |
|
return err; |
|
case GETALL: |
|
case GETVAL: |
|
case GETPID: |
|
case GETNCNT: |
|
case GETZCNT: |
|
case SETALL: |
|
return semctl_main(ns, semid, semnum, cmd, p); |
|
case SETVAL: { |
|
int val; |
|
#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN) |
|
/* big-endian 64bit */ |
|
val = arg >> 32; |
|
#else |
|
/* 32bit or little-endian 64bit */ |
|
val = arg; |
|
#endif |
|
return semctl_setval(ns, semid, semnum, val); |
|
} |
|
case IPC_SET: |
|
if (copy_semid_from_user(&semid64, p, version)) |
|
return -EFAULT; |
|
fallthrough; |
|
case IPC_RMID: |
|
return semctl_down(ns, semid, cmd, &semid64); |
|
default: |
|
return -EINVAL; |
|
} |
|
} |
|
|
|
SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) |
|
{ |
|
return ksys_semctl(semid, semnum, cmd, arg, IPC_64); |
|
} |
|
|
|
#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION |
|
long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg) |
|
{ |
|
int version = ipc_parse_version(&cmd); |
|
|
|
return ksys_semctl(semid, semnum, cmd, arg, version); |
|
} |
|
|
|
SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) |
|
{ |
|
return ksys_old_semctl(semid, semnum, cmd, arg); |
|
} |
|
#endif |
|
|
|
#ifdef CONFIG_COMPAT |
|
|
|
struct compat_semid_ds { |
|
struct compat_ipc_perm sem_perm; |
|
old_time32_t sem_otime; |
|
old_time32_t sem_ctime; |
|
compat_uptr_t sem_base; |
|
compat_uptr_t sem_pending; |
|
compat_uptr_t sem_pending_last; |
|
compat_uptr_t undo; |
|
unsigned short sem_nsems; |
|
}; |
|
|
|
static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf, |
|
int version) |
|
{ |
|
memset(out, 0, sizeof(*out)); |
|
if (version == IPC_64) { |
|
struct compat_semid64_ds __user *p = buf; |
|
return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm); |
|
} else { |
|
struct compat_semid_ds __user *p = buf; |
|
return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm); |
|
} |
|
} |
|
|
|
static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in, |
|
int version) |
|
{ |
|
if (version == IPC_64) { |
|
struct compat_semid64_ds v; |
|
memset(&v, 0, sizeof(v)); |
|
to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm); |
|
v.sem_otime = lower_32_bits(in->sem_otime); |
|
v.sem_otime_high = upper_32_bits(in->sem_otime); |
|
v.sem_ctime = lower_32_bits(in->sem_ctime); |
|
v.sem_ctime_high = upper_32_bits(in->sem_ctime); |
|
v.sem_nsems = in->sem_nsems; |
|
return copy_to_user(buf, &v, sizeof(v)); |
|
} else { |
|
struct compat_semid_ds v; |
|
memset(&v, 0, sizeof(v)); |
|
to_compat_ipc_perm(&v.sem_perm, &in->sem_perm); |
|
v.sem_otime = in->sem_otime; |
|
v.sem_ctime = in->sem_ctime; |
|
v.sem_nsems = in->sem_nsems; |
|
return copy_to_user(buf, &v, sizeof(v)); |
|
} |
|
} |
|
|
|
static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version) |
|
{ |
|
void __user *p = compat_ptr(arg); |
|
struct ipc_namespace *ns; |
|
struct semid64_ds semid64; |
|
int err; |
|
|
|
ns = current->nsproxy->ipc_ns; |
|
|
|
if (semid < 0) |
|
return -EINVAL; |
|
|
|
switch (cmd & (~IPC_64)) { |
|
case IPC_INFO: |
|
case SEM_INFO: |
|
return semctl_info(ns, semid, cmd, p); |
|
case IPC_STAT: |
|
case SEM_STAT: |
|
case SEM_STAT_ANY: |
|
err = semctl_stat(ns, semid, cmd, &semid64); |
|
if (err < 0) |
|
return err; |
|
if (copy_compat_semid_to_user(p, &semid64, version)) |
|
err = -EFAULT; |
|
return err; |
|
case GETVAL: |
|
case GETPID: |
|
case GETNCNT: |
|
case GETZCNT: |
|
case GETALL: |
|
case SETALL: |
|
return semctl_main(ns, semid, semnum, cmd, p); |
|
case SETVAL: |
|
return semctl_setval(ns, semid, semnum, arg); |
|
case IPC_SET: |
|
if (copy_compat_semid_from_user(&semid64, p, version)) |
|
return -EFAULT; |
|
fallthrough; |
|
case IPC_RMID: |
|
return semctl_down(ns, semid, cmd, &semid64); |
|
default: |
|
return -EINVAL; |
|
} |
|
} |
|
|
|
COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg) |
|
{ |
|
return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64); |
|
} |
|
|
|
#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION |
|
long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg) |
|
{ |
|
int version = compat_ipc_parse_version(&cmd); |
|
|
|
return compat_ksys_semctl(semid, semnum, cmd, arg, version); |
|
} |
|
|
|
COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg) |
|
{ |
|
return compat_ksys_old_semctl(semid, semnum, cmd, arg); |
|
} |
|
#endif |
|
#endif |
|
|
|
/* If the task doesn't already have a undo_list, then allocate one |
|
* here. We guarantee there is only one thread using this undo list, |
|
* and current is THE ONE |
|
* |
|
* If this allocation and assignment succeeds, but later |
|
* portions of this code fail, there is no need to free the sem_undo_list. |
|
* Just let it stay associated with the task, and it'll be freed later |
|
* at exit time. |
|
* |
|
* This can block, so callers must hold no locks. |
|
*/ |
|
static inline int get_undo_list(struct sem_undo_list **undo_listp) |
|
{ |
|
struct sem_undo_list *undo_list; |
|
|
|
undo_list = current->sysvsem.undo_list; |
|
if (!undo_list) { |
|
undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL_ACCOUNT); |
|
if (undo_list == NULL) |
|
return -ENOMEM; |
|
spin_lock_init(&undo_list->lock); |
|
refcount_set(&undo_list->refcnt, 1); |
|
INIT_LIST_HEAD(&undo_list->list_proc); |
|
|
|
current->sysvsem.undo_list = undo_list; |
|
} |
|
*undo_listp = undo_list; |
|
return 0; |
|
} |
|
|
|
static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) |
|
{ |
|
struct sem_undo *un; |
|
|
|
list_for_each_entry_rcu(un, &ulp->list_proc, list_proc, |
|
spin_is_locked(&ulp->lock)) { |
|
if (un->semid == semid) |
|
return un; |
|
} |
|
return NULL; |
|
} |
|
|
|
static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) |
|
{ |
|
struct sem_undo *un; |
|
|
|
assert_spin_locked(&ulp->lock); |
|
|
|
un = __lookup_undo(ulp, semid); |
|
if (un) { |
|
list_del_rcu(&un->list_proc); |
|
list_add_rcu(&un->list_proc, &ulp->list_proc); |
|
} |
|
return un; |
|
} |
|
|
|
/** |
|
* find_alloc_undo - lookup (and if not present create) undo array |
|
* @ns: namespace |
|
* @semid: semaphore array id |
|
* |
|
* The function looks up (and if not present creates) the undo structure. |
|
* The size of the undo structure depends on the size of the semaphore |
|
* array, thus the alloc path is not that straightforward. |
|
* Lifetime-rules: sem_undo is rcu-protected, on success, the function |
|
* performs a rcu_read_lock(). |
|
*/ |
|
static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) |
|
{ |
|
struct sem_array *sma; |
|
struct sem_undo_list *ulp; |
|
struct sem_undo *un, *new; |
|
int nsems, error; |
|
|
|
error = get_undo_list(&ulp); |
|
if (error) |
|
return ERR_PTR(error); |
|
|
|
rcu_read_lock(); |
|
spin_lock(&ulp->lock); |
|
un = lookup_undo(ulp, semid); |
|
spin_unlock(&ulp->lock); |
|
if (likely(un != NULL)) |
|
goto out; |
|
|
|
/* no undo structure around - allocate one. */ |
|
/* step 1: figure out the size of the semaphore array */ |
|
sma = sem_obtain_object_check(ns, semid); |
|
if (IS_ERR(sma)) { |
|
rcu_read_unlock(); |
|
return ERR_CAST(sma); |
|
} |
|
|
|
nsems = sma->sem_nsems; |
|
if (!ipc_rcu_getref(&sma->sem_perm)) { |
|
rcu_read_unlock(); |
|
un = ERR_PTR(-EIDRM); |
|
goto out; |
|
} |
|
rcu_read_unlock(); |
|
|
|
/* step 2: allocate new undo structure */ |
|
new = kvzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, |
|
GFP_KERNEL_ACCOUNT); |
|
if (!new) { |
|
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
|
return ERR_PTR(-ENOMEM); |
|
} |
|
|
|
/* step 3: Acquire the lock on semaphore array */ |
|
rcu_read_lock(); |
|
sem_lock_and_putref(sma); |
|
if (!ipc_valid_object(&sma->sem_perm)) { |
|
sem_unlock(sma, -1); |
|
rcu_read_unlock(); |
|
kvfree(new); |
|
un = ERR_PTR(-EIDRM); |
|
goto out; |
|
} |
|
spin_lock(&ulp->lock); |
|
|
|
/* |
|
* step 4: check for races: did someone else allocate the undo struct? |
|
*/ |
|
un = lookup_undo(ulp, semid); |
|
if (un) { |
|
kvfree(new); |
|
goto success; |
|
} |
|
/* step 5: initialize & link new undo structure */ |
|
new->semadj = (short *) &new[1]; |
|
new->ulp = ulp; |
|
new->semid = semid; |
|
assert_spin_locked(&ulp->lock); |
|
list_add_rcu(&new->list_proc, &ulp->list_proc); |
|
ipc_assert_locked_object(&sma->sem_perm); |
|
list_add(&new->list_id, &sma->list_id); |
|
un = new; |
|
|
|
success: |
|
spin_unlock(&ulp->lock); |
|
sem_unlock(sma, -1); |
|
out: |
|
return un; |
|
} |
|
|
|
long __do_semtimedop(int semid, struct sembuf *sops, |
|
unsigned nsops, const struct timespec64 *timeout, |
|
struct ipc_namespace *ns) |
|
{ |
|
int error = -EINVAL; |
|
struct sem_array *sma; |
|
struct sembuf *sop; |
|
struct sem_undo *un; |
|
int max, locknum; |
|
bool undos = false, alter = false, dupsop = false; |
|
struct sem_queue queue; |
|
unsigned long dup = 0, jiffies_left = 0; |
|
|
|
if (nsops < 1 || semid < 0) |
|
return -EINVAL; |
|
if (nsops > ns->sc_semopm) |
|
return -E2BIG; |
|
|
|
if (timeout) { |
|
if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 || |
|
timeout->tv_nsec >= 1000000000L) { |
|
error = -EINVAL; |
|
goto out; |
|
} |
|
jiffies_left = timespec64_to_jiffies(timeout); |
|
} |
|
|
|
|
|
max = 0; |
|
for (sop = sops; sop < sops + nsops; sop++) { |
|
unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG); |
|
|
|
if (sop->sem_num >= max) |
|
max = sop->sem_num; |
|
if (sop->sem_flg & SEM_UNDO) |
|
undos = true; |
|
if (dup & mask) { |
|
/* |
|
* There was a previous alter access that appears |
|
* to have accessed the same semaphore, thus use |
|
* the dupsop logic. "appears", because the detection |
|
* can only check % BITS_PER_LONG. |
|
*/ |
|
dupsop = true; |
|
} |
|
if (sop->sem_op != 0) { |
|
alter = true; |
|
dup |= mask; |
|
} |
|
} |
|
|
|
if (undos) { |
|
/* On success, find_alloc_undo takes the rcu_read_lock */ |
|
un = find_alloc_undo(ns, semid); |
|
if (IS_ERR(un)) { |
|
error = PTR_ERR(un); |
|
goto out; |
|
} |
|
} else { |
|
un = NULL; |
|
rcu_read_lock(); |
|
} |
|
|
|
sma = sem_obtain_object_check(ns, semid); |
|
if (IS_ERR(sma)) { |
|
rcu_read_unlock(); |
|
error = PTR_ERR(sma); |
|
goto out; |
|
} |
|
|
|
error = -EFBIG; |
|
if (max >= sma->sem_nsems) { |
|
rcu_read_unlock(); |
|
goto out; |
|
} |
|
|
|
error = -EACCES; |
|
if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) { |
|
rcu_read_unlock(); |
|
goto out; |
|
} |
|
|
|
error = security_sem_semop(&sma->sem_perm, sops, nsops, alter); |
|
if (error) { |
|
rcu_read_unlock(); |
|
goto out; |
|
} |
|
|
|
error = -EIDRM; |
|
locknum = sem_lock(sma, sops, nsops); |
|
/* |
|
* We eventually might perform the following check in a lockless |
|
* fashion, considering ipc_valid_object() locking constraints. |
|
* If nsops == 1 and there is no contention for sem_perm.lock, then |
|
* only a per-semaphore lock is held and it's OK to proceed with the |
|
* check below. More details on the fine grained locking scheme |
|
* entangled here and why it's RMID race safe on comments at sem_lock() |
|
*/ |
|
if (!ipc_valid_object(&sma->sem_perm)) |
|
goto out_unlock; |
|
/* |
|
* semid identifiers are not unique - find_alloc_undo may have |
|
* allocated an undo structure, it was invalidated by an RMID |
|
* and now a new array with received the same id. Check and fail. |
|
* This case can be detected checking un->semid. The existence of |
|
* "un" itself is guaranteed by rcu. |
|
*/ |
|
if (un && un->semid == -1) |
|
goto out_unlock; |
|
|
|
queue.sops = sops; |
|
queue.nsops = nsops; |
|
queue.undo = un; |
|
queue.pid = task_tgid(current); |
|
queue.alter = alter; |
|
queue.dupsop = dupsop; |
|
|
|
error = perform_atomic_semop(sma, &queue); |
|
if (error == 0) { /* non-blocking successful path */ |
|
DEFINE_WAKE_Q(wake_q); |
|
|
|
/* |
|
* If the operation was successful, then do |
|
* the required updates. |
|
*/ |
|
if (alter) |
|
do_smart_update(sma, sops, nsops, 1, &wake_q); |
|
else |
|
set_semotime(sma, sops); |
|
|
|
sem_unlock(sma, locknum); |
|
rcu_read_unlock(); |
|
wake_up_q(&wake_q); |
|
|
|
goto out; |
|
} |
|
if (error < 0) /* non-blocking error path */ |
|
goto out_unlock; |
|
|
|
/* |
|
* We need to sleep on this operation, so we put the current |
|
* task into the pending queue and go to sleep. |
|
*/ |
|
if (nsops == 1) { |
|
struct sem *curr; |
|
int idx = array_index_nospec(sops->sem_num, sma->sem_nsems); |
|
curr = &sma->sems[idx]; |
|
|
|
if (alter) { |
|
if (sma->complex_count) { |
|
list_add_tail(&queue.list, |
|
&sma->pending_alter); |
|
} else { |
|
|
|
list_add_tail(&queue.list, |
|
&curr->pending_alter); |
|
} |
|
} else { |
|
list_add_tail(&queue.list, &curr->pending_const); |
|
} |
|
} else { |
|
if (!sma->complex_count) |
|
merge_queues(sma); |
|
|
|
if (alter) |
|
list_add_tail(&queue.list, &sma->pending_alter); |
|
else |
|
list_add_tail(&queue.list, &sma->pending_const); |
|
|
|
sma->complex_count++; |
|
} |
|
|
|
do { |
|
/* memory ordering ensured by the lock in sem_lock() */ |
|
WRITE_ONCE(queue.status, -EINTR); |
|
queue.sleeper = current; |
|
|
|
/* memory ordering is ensured by the lock in sem_lock() */ |
|
__set_current_state(TASK_INTERRUPTIBLE); |
|
sem_unlock(sma, locknum); |
|
rcu_read_unlock(); |
|
|
|
if (timeout) |
|
jiffies_left = schedule_timeout(jiffies_left); |
|
else |
|
schedule(); |
|
|
|
/* |
|
* fastpath: the semop has completed, either successfully or |
|
* not, from the syscall pov, is quite irrelevant to us at this |
|
* point; we're done. |
|
* |
|
* We _do_ care, nonetheless, about being awoken by a signal or |
|
* spuriously. The queue.status is checked again in the |
|
* slowpath (aka after taking sem_lock), such that we can detect |
|
* scenarios where we were awakened externally, during the |
|
* window between wake_q_add() and wake_up_q(). |
|
*/ |
|
error = READ_ONCE(queue.status); |
|
if (error != -EINTR) { |
|
/* see SEM_BARRIER_2 for purpose/pairing */ |
|
smp_acquire__after_ctrl_dep(); |
|
goto out; |
|
} |
|
|
|
rcu_read_lock(); |
|
locknum = sem_lock(sma, sops, nsops); |
|
|
|
if (!ipc_valid_object(&sma->sem_perm)) |
|
goto out_unlock; |
|
|
|
/* |
|
* No necessity for any barrier: We are protect by sem_lock() |
|
*/ |
|
error = READ_ONCE(queue.status); |
|
|
|
/* |
|
* If queue.status != -EINTR we are woken up by another process. |
|
* Leave without unlink_queue(), but with sem_unlock(). |
|
*/ |
|
if (error != -EINTR) |
|
goto out_unlock; |
|
|
|
/* |
|
* If an interrupt occurred we have to clean up the queue. |
|
*/ |
|
if (timeout && jiffies_left == 0) |
|
error = -EAGAIN; |
|
} while (error == -EINTR && !signal_pending(current)); /* spurious */ |
|
|
|
unlink_queue(sma, &queue); |
|
|
|
out_unlock: |
|
sem_unlock(sma, locknum); |
|
rcu_read_unlock(); |
|
out: |
|
return error; |
|
} |
|
|
|
static long do_semtimedop(int semid, struct sembuf __user *tsops, |
|
unsigned nsops, const struct timespec64 *timeout) |
|
{ |
|
struct sembuf fast_sops[SEMOPM_FAST]; |
|
struct sembuf *sops = fast_sops; |
|
struct ipc_namespace *ns; |
|
int ret; |
|
|
|
ns = current->nsproxy->ipc_ns; |
|
if (nsops > ns->sc_semopm) |
|
return -E2BIG; |
|
if (nsops < 1) |
|
return -EINVAL; |
|
|
|
if (nsops > SEMOPM_FAST) { |
|
sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL); |
|
if (sops == NULL) |
|
return -ENOMEM; |
|
} |
|
|
|
if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) { |
|
ret = -EFAULT; |
|
goto out_free; |
|
} |
|
|
|
ret = __do_semtimedop(semid, sops, nsops, timeout, ns); |
|
|
|
out_free: |
|
if (sops != fast_sops) |
|
kvfree(sops); |
|
|
|
return ret; |
|
} |
|
|
|
long ksys_semtimedop(int semid, struct sembuf __user *tsops, |
|
unsigned int nsops, const struct __kernel_timespec __user *timeout) |
|
{ |
|
if (timeout) { |
|
struct timespec64 ts; |
|
if (get_timespec64(&ts, timeout)) |
|
return -EFAULT; |
|
return do_semtimedop(semid, tsops, nsops, &ts); |
|
} |
|
return do_semtimedop(semid, tsops, nsops, NULL); |
|
} |
|
|
|
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, |
|
unsigned int, nsops, const struct __kernel_timespec __user *, timeout) |
|
{ |
|
return ksys_semtimedop(semid, tsops, nsops, timeout); |
|
} |
|
|
|
#ifdef CONFIG_COMPAT_32BIT_TIME |
|
long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems, |
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unsigned int nsops, |
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const struct old_timespec32 __user *timeout) |
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{ |
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if (timeout) { |
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struct timespec64 ts; |
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if (get_old_timespec32(&ts, timeout)) |
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return -EFAULT; |
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return do_semtimedop(semid, tsems, nsops, &ts); |
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} |
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return do_semtimedop(semid, tsems, nsops, NULL); |
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} |
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SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems, |
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unsigned int, nsops, |
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const struct old_timespec32 __user *, timeout) |
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{ |
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return compat_ksys_semtimedop(semid, tsems, nsops, timeout); |
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} |
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#endif |
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SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, |
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unsigned, nsops) |
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{ |
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return do_semtimedop(semid, tsops, nsops, NULL); |
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} |
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/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between |
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* parent and child tasks. |
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*/ |
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int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) |
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{ |
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struct sem_undo_list *undo_list; |
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int error; |
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if (clone_flags & CLONE_SYSVSEM) { |
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error = get_undo_list(&undo_list); |
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if (error) |
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return error; |
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refcount_inc(&undo_list->refcnt); |
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tsk->sysvsem.undo_list = undo_list; |
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} else |
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tsk->sysvsem.undo_list = NULL; |
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return 0; |
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} |
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/* |
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* add semadj values to semaphores, free undo structures. |
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* undo structures are not freed when semaphore arrays are destroyed |
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* so some of them may be out of date. |
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* IMPLEMENTATION NOTE: There is some confusion over whether the |
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* set of adjustments that needs to be done should be done in an atomic |
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* manner or not. That is, if we are attempting to decrement the semval |
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* should we queue up and wait until we can do so legally? |
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* The original implementation attempted to do this (queue and wait). |
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* The current implementation does not do so. The POSIX standard |
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* and SVID should be consulted to determine what behavior is mandated. |
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*/ |
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void exit_sem(struct task_struct *tsk) |
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{ |
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struct sem_undo_list *ulp; |
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ulp = tsk->sysvsem.undo_list; |
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if (!ulp) |
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return; |
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tsk->sysvsem.undo_list = NULL; |
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if (!refcount_dec_and_test(&ulp->refcnt)) |
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return; |
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for (;;) { |
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struct sem_array *sma; |
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struct sem_undo *un; |
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int semid, i; |
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DEFINE_WAKE_Q(wake_q); |
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cond_resched(); |
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rcu_read_lock(); |
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un = list_entry_rcu(ulp->list_proc.next, |
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struct sem_undo, list_proc); |
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if (&un->list_proc == &ulp->list_proc) { |
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/* |
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* We must wait for freeary() before freeing this ulp, |
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* in case we raced with last sem_undo. There is a small |
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* possibility where we exit while freeary() didn't |
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* finish unlocking sem_undo_list. |
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*/ |
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spin_lock(&ulp->lock); |
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spin_unlock(&ulp->lock); |
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rcu_read_unlock(); |
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break; |
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} |
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spin_lock(&ulp->lock); |
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semid = un->semid; |
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spin_unlock(&ulp->lock); |
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/* exit_sem raced with IPC_RMID, nothing to do */ |
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if (semid == -1) { |
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rcu_read_unlock(); |
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continue; |
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} |
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sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid); |
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/* exit_sem raced with IPC_RMID, nothing to do */ |
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if (IS_ERR(sma)) { |
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rcu_read_unlock(); |
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continue; |
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} |
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sem_lock(sma, NULL, -1); |
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/* exit_sem raced with IPC_RMID, nothing to do */ |
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if (!ipc_valid_object(&sma->sem_perm)) { |
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sem_unlock(sma, -1); |
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rcu_read_unlock(); |
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continue; |
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} |
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un = __lookup_undo(ulp, semid); |
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if (un == NULL) { |
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/* exit_sem raced with IPC_RMID+semget() that created |
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* exactly the same semid. Nothing to do. |
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*/ |
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sem_unlock(sma, -1); |
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rcu_read_unlock(); |
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continue; |
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} |
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/* remove un from the linked lists */ |
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ipc_assert_locked_object(&sma->sem_perm); |
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list_del(&un->list_id); |
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spin_lock(&ulp->lock); |
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list_del_rcu(&un->list_proc); |
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spin_unlock(&ulp->lock); |
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/* perform adjustments registered in un */ |
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for (i = 0; i < sma->sem_nsems; i++) { |
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struct sem *semaphore = &sma->sems[i]; |
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if (un->semadj[i]) { |
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semaphore->semval += un->semadj[i]; |
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/* |
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* Range checks of the new semaphore value, |
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* not defined by sus: |
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* - Some unices ignore the undo entirely |
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* (e.g. HP UX 11i 11.22, Tru64 V5.1) |
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* - some cap the value (e.g. FreeBSD caps |
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* at 0, but doesn't enforce SEMVMX) |
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* |
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* Linux caps the semaphore value, both at 0 |
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* and at SEMVMX. |
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* |
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* Manfred <[email protected]> |
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*/ |
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if (semaphore->semval < 0) |
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semaphore->semval = 0; |
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if (semaphore->semval > SEMVMX) |
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semaphore->semval = SEMVMX; |
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ipc_update_pid(&semaphore->sempid, task_tgid(current)); |
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} |
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} |
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/* maybe some queued-up processes were waiting for this */ |
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do_smart_update(sma, NULL, 0, 1, &wake_q); |
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sem_unlock(sma, -1); |
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rcu_read_unlock(); |
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wake_up_q(&wake_q); |
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|
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kvfree_rcu(un, rcu); |
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} |
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kfree(ulp); |
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} |
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#ifdef CONFIG_PROC_FS |
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static int sysvipc_sem_proc_show(struct seq_file *s, void *it) |
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{ |
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struct user_namespace *user_ns = seq_user_ns(s); |
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struct kern_ipc_perm *ipcp = it; |
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struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
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time64_t sem_otime; |
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|
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/* |
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* The proc interface isn't aware of sem_lock(), it calls |
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* ipc_lock_object(), i.e. spin_lock(&sma->sem_perm.lock). |
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* (in sysvipc_find_ipc) |
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* In order to stay compatible with sem_lock(), we must |
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* enter / leave complex_mode. |
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*/ |
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complexmode_enter(sma); |
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sem_otime = get_semotime(sma); |
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|
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seq_printf(s, |
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"%10d %10d %4o %10u %5u %5u %5u %5u %10llu %10llu\n", |
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sma->sem_perm.key, |
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sma->sem_perm.id, |
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sma->sem_perm.mode, |
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sma->sem_nsems, |
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from_kuid_munged(user_ns, sma->sem_perm.uid), |
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from_kgid_munged(user_ns, sma->sem_perm.gid), |
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from_kuid_munged(user_ns, sma->sem_perm.cuid), |
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from_kgid_munged(user_ns, sma->sem_perm.cgid), |
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sem_otime, |
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sma->sem_ctime); |
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complexmode_tryleave(sma); |
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|
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return 0; |
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} |
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#endif
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