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374 lines
9.6 KiB
374 lines
9.6 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* KASAN quarantine. |
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* |
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* Author: Alexander Potapenko <[email protected]> |
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* Copyright (C) 2016 Google, Inc. |
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* |
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* Based on code by Dmitry Chernenkov. |
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*/ |
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#include <linux/gfp.h> |
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#include <linux/hash.h> |
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#include <linux/kernel.h> |
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#include <linux/mm.h> |
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#include <linux/percpu.h> |
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#include <linux/printk.h> |
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#include <linux/shrinker.h> |
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#include <linux/slab.h> |
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#include <linux/srcu.h> |
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#include <linux/string.h> |
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#include <linux/types.h> |
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#include <linux/cpuhotplug.h> |
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#include "../slab.h" |
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#include "kasan.h" |
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/* Data structure and operations for quarantine queues. */ |
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/* |
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* Each queue is a single-linked list, which also stores the total size of |
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* objects inside of it. |
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*/ |
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struct qlist_head { |
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struct qlist_node *head; |
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struct qlist_node *tail; |
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size_t bytes; |
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bool offline; |
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}; |
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#define QLIST_INIT { NULL, NULL, 0 } |
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static bool qlist_empty(struct qlist_head *q) |
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{ |
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return !q->head; |
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} |
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static void qlist_init(struct qlist_head *q) |
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{ |
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q->head = q->tail = NULL; |
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q->bytes = 0; |
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} |
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static void qlist_put(struct qlist_head *q, struct qlist_node *qlink, |
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size_t size) |
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{ |
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if (unlikely(qlist_empty(q))) |
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q->head = qlink; |
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else |
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q->tail->next = qlink; |
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q->tail = qlink; |
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qlink->next = NULL; |
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q->bytes += size; |
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} |
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static void qlist_move_all(struct qlist_head *from, struct qlist_head *to) |
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{ |
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if (unlikely(qlist_empty(from))) |
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return; |
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if (qlist_empty(to)) { |
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*to = *from; |
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qlist_init(from); |
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return; |
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} |
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to->tail->next = from->head; |
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to->tail = from->tail; |
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to->bytes += from->bytes; |
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qlist_init(from); |
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} |
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#define QUARANTINE_PERCPU_SIZE (1 << 20) |
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#define QUARANTINE_BATCHES \ |
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(1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS) |
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/* |
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* The object quarantine consists of per-cpu queues and a global queue, |
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* guarded by quarantine_lock. |
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*/ |
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static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); |
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/* Round-robin FIFO array of batches. */ |
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static struct qlist_head global_quarantine[QUARANTINE_BATCHES]; |
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static int quarantine_head; |
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static int quarantine_tail; |
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/* Total size of all objects in global_quarantine across all batches. */ |
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static unsigned long quarantine_size; |
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static DEFINE_RAW_SPINLOCK(quarantine_lock); |
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DEFINE_STATIC_SRCU(remove_cache_srcu); |
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/* Maximum size of the global queue. */ |
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static unsigned long quarantine_max_size; |
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/* |
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* Target size of a batch in global_quarantine. |
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* Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM. |
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*/ |
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static unsigned long quarantine_batch_size; |
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/* |
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* The fraction of physical memory the quarantine is allowed to occupy. |
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* Quarantine doesn't support memory shrinker with SLAB allocator, so we keep |
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* the ratio low to avoid OOM. |
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*/ |
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#define QUARANTINE_FRACTION 32 |
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static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink) |
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{ |
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return virt_to_head_page(qlink)->slab_cache; |
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} |
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static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) |
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{ |
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struct kasan_free_meta *free_info = |
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container_of(qlink, struct kasan_free_meta, |
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quarantine_link); |
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return ((void *)free_info) - cache->kasan_info.free_meta_offset; |
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} |
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static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) |
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{ |
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void *object = qlink_to_object(qlink, cache); |
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unsigned long flags; |
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if (IS_ENABLED(CONFIG_SLAB)) |
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local_irq_save(flags); |
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/* |
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* As the object now gets freed from the quarantine, assume that its |
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* free track is no longer valid. |
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*/ |
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*(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE; |
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___cache_free(cache, object, _THIS_IP_); |
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if (IS_ENABLED(CONFIG_SLAB)) |
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local_irq_restore(flags); |
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} |
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static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) |
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{ |
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struct qlist_node *qlink; |
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if (unlikely(qlist_empty(q))) |
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return; |
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qlink = q->head; |
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while (qlink) { |
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struct kmem_cache *obj_cache = |
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cache ? cache : qlink_to_cache(qlink); |
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struct qlist_node *next = qlink->next; |
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qlink_free(qlink, obj_cache); |
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qlink = next; |
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} |
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qlist_init(q); |
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} |
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bool kasan_quarantine_put(struct kmem_cache *cache, void *object) |
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{ |
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unsigned long flags; |
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struct qlist_head *q; |
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struct qlist_head temp = QLIST_INIT; |
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struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); |
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/* |
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* If there's no metadata for this object, don't put it into |
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* quarantine. |
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*/ |
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if (!meta) |
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return false; |
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/* |
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* Note: irq must be disabled until after we move the batch to the |
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* global quarantine. Otherwise kasan_quarantine_remove_cache() can |
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* miss some objects belonging to the cache if they are in our local |
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* temp list. kasan_quarantine_remove_cache() executes on_each_cpu() |
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* at the beginning which ensures that it either sees the objects in |
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* per-cpu lists or in the global quarantine. |
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*/ |
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local_irq_save(flags); |
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q = this_cpu_ptr(&cpu_quarantine); |
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if (q->offline) { |
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local_irq_restore(flags); |
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return false; |
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} |
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qlist_put(q, &meta->quarantine_link, cache->size); |
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if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { |
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qlist_move_all(q, &temp); |
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raw_spin_lock(&quarantine_lock); |
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WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes); |
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qlist_move_all(&temp, &global_quarantine[quarantine_tail]); |
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if (global_quarantine[quarantine_tail].bytes >= |
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READ_ONCE(quarantine_batch_size)) { |
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int new_tail; |
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new_tail = quarantine_tail + 1; |
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if (new_tail == QUARANTINE_BATCHES) |
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new_tail = 0; |
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if (new_tail != quarantine_head) |
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quarantine_tail = new_tail; |
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} |
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raw_spin_unlock(&quarantine_lock); |
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} |
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local_irq_restore(flags); |
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return true; |
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} |
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void kasan_quarantine_reduce(void) |
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{ |
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size_t total_size, new_quarantine_size, percpu_quarantines; |
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unsigned long flags; |
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int srcu_idx; |
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struct qlist_head to_free = QLIST_INIT; |
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if (likely(READ_ONCE(quarantine_size) <= |
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READ_ONCE(quarantine_max_size))) |
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return; |
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/* |
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* srcu critical section ensures that kasan_quarantine_remove_cache() |
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* will not miss objects belonging to the cache while they are in our |
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* local to_free list. srcu is chosen because (1) it gives us private |
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* grace period domain that does not interfere with anything else, |
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* and (2) it allows synchronize_srcu() to return without waiting |
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* if there are no pending read critical sections (which is the |
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* expected case). |
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*/ |
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srcu_idx = srcu_read_lock(&remove_cache_srcu); |
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raw_spin_lock_irqsave(&quarantine_lock, flags); |
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/* |
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* Update quarantine size in case of hotplug. Allocate a fraction of |
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* the installed memory to quarantine minus per-cpu queue limits. |
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*/ |
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total_size = (totalram_pages() << PAGE_SHIFT) / |
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QUARANTINE_FRACTION; |
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percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); |
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new_quarantine_size = (total_size < percpu_quarantines) ? |
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0 : total_size - percpu_quarantines; |
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WRITE_ONCE(quarantine_max_size, new_quarantine_size); |
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/* Aim at consuming at most 1/2 of slots in quarantine. */ |
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WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE, |
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2 * total_size / QUARANTINE_BATCHES)); |
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if (likely(quarantine_size > quarantine_max_size)) { |
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qlist_move_all(&global_quarantine[quarantine_head], &to_free); |
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WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes); |
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quarantine_head++; |
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if (quarantine_head == QUARANTINE_BATCHES) |
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quarantine_head = 0; |
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} |
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raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
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qlist_free_all(&to_free, NULL); |
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srcu_read_unlock(&remove_cache_srcu, srcu_idx); |
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} |
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static void qlist_move_cache(struct qlist_head *from, |
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struct qlist_head *to, |
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struct kmem_cache *cache) |
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{ |
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struct qlist_node *curr; |
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if (unlikely(qlist_empty(from))) |
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return; |
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curr = from->head; |
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qlist_init(from); |
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while (curr) { |
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struct qlist_node *next = curr->next; |
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struct kmem_cache *obj_cache = qlink_to_cache(curr); |
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if (obj_cache == cache) |
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qlist_put(to, curr, obj_cache->size); |
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else |
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qlist_put(from, curr, obj_cache->size); |
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curr = next; |
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} |
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} |
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static void per_cpu_remove_cache(void *arg) |
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{ |
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struct kmem_cache *cache = arg; |
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struct qlist_head to_free = QLIST_INIT; |
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struct qlist_head *q; |
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q = this_cpu_ptr(&cpu_quarantine); |
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qlist_move_cache(q, &to_free, cache); |
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qlist_free_all(&to_free, cache); |
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} |
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/* Free all quarantined objects belonging to cache. */ |
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void kasan_quarantine_remove_cache(struct kmem_cache *cache) |
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{ |
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unsigned long flags, i; |
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struct qlist_head to_free = QLIST_INIT; |
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/* |
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* Must be careful to not miss any objects that are being moved from |
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* per-cpu list to the global quarantine in kasan_quarantine_put(), |
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* nor objects being freed in kasan_quarantine_reduce(). on_each_cpu() |
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* achieves the first goal, while synchronize_srcu() achieves the |
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* second. |
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*/ |
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on_each_cpu(per_cpu_remove_cache, cache, 1); |
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raw_spin_lock_irqsave(&quarantine_lock, flags); |
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for (i = 0; i < QUARANTINE_BATCHES; i++) { |
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if (qlist_empty(&global_quarantine[i])) |
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continue; |
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qlist_move_cache(&global_quarantine[i], &to_free, cache); |
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/* Scanning whole quarantine can take a while. */ |
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raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
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cond_resched(); |
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raw_spin_lock_irqsave(&quarantine_lock, flags); |
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} |
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raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
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qlist_free_all(&to_free, cache); |
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synchronize_srcu(&remove_cache_srcu); |
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} |
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static int kasan_cpu_online(unsigned int cpu) |
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{ |
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this_cpu_ptr(&cpu_quarantine)->offline = false; |
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return 0; |
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} |
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static int kasan_cpu_offline(unsigned int cpu) |
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{ |
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struct qlist_head *q; |
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q = this_cpu_ptr(&cpu_quarantine); |
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/* Ensure the ordering between the writing to q->offline and |
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* qlist_free_all. Otherwise, cpu_quarantine may be corrupted |
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* by interrupt. |
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*/ |
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WRITE_ONCE(q->offline, true); |
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barrier(); |
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qlist_free_all(q, NULL); |
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return 0; |
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} |
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static int __init kasan_cpu_quarantine_init(void) |
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{ |
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int ret = 0; |
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ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online", |
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kasan_cpu_online, kasan_cpu_offline); |
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if (ret < 0) |
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pr_err("kasan cpu quarantine register failed [%d]\n", ret); |
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return ret; |
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} |
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late_initcall(kasan_cpu_quarantine_init);
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