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304 lines
8.2 KiB
304 lines
8.2 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* linux/mm/process_vm_access.c |
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* |
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* Copyright (C) 2010-2011 Christopher Yeoh <[email protected]>, IBM Corp. |
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*/ |
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#include <linux/compat.h> |
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#include <linux/mm.h> |
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#include <linux/uio.h> |
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#include <linux/sched.h> |
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#include <linux/sched/mm.h> |
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#include <linux/highmem.h> |
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#include <linux/ptrace.h> |
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#include <linux/slab.h> |
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#include <linux/syscalls.h> |
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/** |
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* process_vm_rw_pages - read/write pages from task specified |
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* @pages: array of pointers to pages we want to copy |
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* @offset: offset in page to start copying from/to |
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* @len: number of bytes to copy |
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* @iter: where to copy to/from locally |
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* @vm_write: 0 means copy from, 1 means copy to |
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* Returns 0 on success, error code otherwise |
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*/ |
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static int process_vm_rw_pages(struct page **pages, |
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unsigned offset, |
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size_t len, |
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struct iov_iter *iter, |
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int vm_write) |
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{ |
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/* Do the copy for each page */ |
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while (len && iov_iter_count(iter)) { |
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struct page *page = *pages++; |
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size_t copy = PAGE_SIZE - offset; |
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size_t copied; |
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if (copy > len) |
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copy = len; |
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if (vm_write) |
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copied = copy_page_from_iter(page, offset, copy, iter); |
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else |
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copied = copy_page_to_iter(page, offset, copy, iter); |
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len -= copied; |
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if (copied < copy && iov_iter_count(iter)) |
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return -EFAULT; |
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offset = 0; |
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} |
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return 0; |
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} |
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/* Maximum number of pages kmalloc'd to hold struct page's during copy */ |
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#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2) |
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/** |
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* process_vm_rw_single_vec - read/write pages from task specified |
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* @addr: start memory address of target process |
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* @len: size of area to copy to/from |
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* @iter: where to copy to/from locally |
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* @process_pages: struct pages area that can store at least |
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* nr_pages_to_copy struct page pointers |
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* @mm: mm for task |
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* @task: task to read/write from |
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* @vm_write: 0 means copy from, 1 means copy to |
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* Returns 0 on success or on failure error code |
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*/ |
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static int process_vm_rw_single_vec(unsigned long addr, |
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unsigned long len, |
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struct iov_iter *iter, |
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struct page **process_pages, |
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struct mm_struct *mm, |
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struct task_struct *task, |
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int vm_write) |
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{ |
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unsigned long pa = addr & PAGE_MASK; |
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unsigned long start_offset = addr - pa; |
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unsigned long nr_pages; |
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ssize_t rc = 0; |
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unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES |
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/ sizeof(struct pages *); |
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unsigned int flags = 0; |
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/* Work out address and page range required */ |
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if (len == 0) |
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return 0; |
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nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; |
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if (vm_write) |
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flags |= FOLL_WRITE; |
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while (!rc && nr_pages && iov_iter_count(iter)) { |
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int pinned_pages = min(nr_pages, max_pages_per_loop); |
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int locked = 1; |
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size_t bytes; |
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/* |
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* Get the pages we're interested in. We must |
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* access remotely because task/mm might not |
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* current/current->mm |
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*/ |
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mmap_read_lock(mm); |
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pinned_pages = pin_user_pages_remote(mm, pa, pinned_pages, |
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flags, process_pages, |
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NULL, &locked); |
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if (locked) |
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mmap_read_unlock(mm); |
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if (pinned_pages <= 0) |
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return -EFAULT; |
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bytes = pinned_pages * PAGE_SIZE - start_offset; |
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if (bytes > len) |
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bytes = len; |
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rc = process_vm_rw_pages(process_pages, |
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start_offset, bytes, iter, |
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vm_write); |
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len -= bytes; |
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start_offset = 0; |
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nr_pages -= pinned_pages; |
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pa += pinned_pages * PAGE_SIZE; |
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/* If vm_write is set, the pages need to be made dirty: */ |
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unpin_user_pages_dirty_lock(process_pages, pinned_pages, |
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vm_write); |
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} |
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return rc; |
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} |
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/* Maximum number of entries for process pages array |
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which lives on stack */ |
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#define PVM_MAX_PP_ARRAY_COUNT 16 |
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/** |
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* process_vm_rw_core - core of reading/writing pages from task specified |
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* @pid: PID of process to read/write from/to |
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* @iter: where to copy to/from locally |
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* @rvec: iovec array specifying where to copy to/from in the other process |
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* @riovcnt: size of rvec array |
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* @flags: currently unused |
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* @vm_write: 0 if reading from other process, 1 if writing to other process |
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* |
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* Returns the number of bytes read/written or error code. May |
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* return less bytes than expected if an error occurs during the copying |
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* process. |
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*/ |
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static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, |
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const struct iovec *rvec, |
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unsigned long riovcnt, |
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unsigned long flags, int vm_write) |
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{ |
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struct task_struct *task; |
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struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; |
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struct page **process_pages = pp_stack; |
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struct mm_struct *mm; |
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unsigned long i; |
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ssize_t rc = 0; |
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unsigned long nr_pages = 0; |
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unsigned long nr_pages_iov; |
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ssize_t iov_len; |
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size_t total_len = iov_iter_count(iter); |
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/* |
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* Work out how many pages of struct pages we're going to need |
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* when eventually calling get_user_pages |
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*/ |
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for (i = 0; i < riovcnt; i++) { |
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iov_len = rvec[i].iov_len; |
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if (iov_len > 0) { |
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nr_pages_iov = ((unsigned long)rvec[i].iov_base |
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+ iov_len) |
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/ PAGE_SIZE - (unsigned long)rvec[i].iov_base |
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/ PAGE_SIZE + 1; |
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nr_pages = max(nr_pages, nr_pages_iov); |
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} |
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} |
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if (nr_pages == 0) |
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return 0; |
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if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { |
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/* For reliability don't try to kmalloc more than |
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2 pages worth */ |
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process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, |
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sizeof(struct pages *)*nr_pages), |
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GFP_KERNEL); |
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if (!process_pages) |
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return -ENOMEM; |
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} |
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/* Get process information */ |
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task = find_get_task_by_vpid(pid); |
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if (!task) { |
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rc = -ESRCH; |
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goto free_proc_pages; |
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} |
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mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); |
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if (!mm || IS_ERR(mm)) { |
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rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; |
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/* |
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* Explicitly map EACCES to EPERM as EPERM is a more |
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* appropriate error code for process_vw_readv/writev |
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*/ |
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if (rc == -EACCES) |
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rc = -EPERM; |
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goto put_task_struct; |
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} |
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for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++) |
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rc = process_vm_rw_single_vec( |
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(unsigned long)rvec[i].iov_base, rvec[i].iov_len, |
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iter, process_pages, mm, task, vm_write); |
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/* copied = space before - space after */ |
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total_len -= iov_iter_count(iter); |
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/* If we have managed to copy any data at all then |
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we return the number of bytes copied. Otherwise |
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we return the error code */ |
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if (total_len) |
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rc = total_len; |
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mmput(mm); |
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put_task_struct: |
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put_task_struct(task); |
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free_proc_pages: |
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if (process_pages != pp_stack) |
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kfree(process_pages); |
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return rc; |
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} |
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/** |
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* process_vm_rw - check iovecs before calling core routine |
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* @pid: PID of process to read/write from/to |
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* @lvec: iovec array specifying where to copy to/from locally |
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* @liovcnt: size of lvec array |
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* @rvec: iovec array specifying where to copy to/from in the other process |
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* @riovcnt: size of rvec array |
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* @flags: currently unused |
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* @vm_write: 0 if reading from other process, 1 if writing to other process |
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* |
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* Returns the number of bytes read/written or error code. May |
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* return less bytes than expected if an error occurs during the copying |
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* process. |
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*/ |
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static ssize_t process_vm_rw(pid_t pid, |
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const struct iovec __user *lvec, |
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unsigned long liovcnt, |
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const struct iovec __user *rvec, |
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unsigned long riovcnt, |
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unsigned long flags, int vm_write) |
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{ |
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struct iovec iovstack_l[UIO_FASTIOV]; |
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struct iovec iovstack_r[UIO_FASTIOV]; |
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struct iovec *iov_l = iovstack_l; |
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struct iovec *iov_r; |
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struct iov_iter iter; |
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ssize_t rc; |
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int dir = vm_write ? WRITE : READ; |
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if (flags != 0) |
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return -EINVAL; |
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/* Check iovecs */ |
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rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); |
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if (rc < 0) |
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return rc; |
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if (!iov_iter_count(&iter)) |
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goto free_iov_l; |
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iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, |
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in_compat_syscall()); |
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if (IS_ERR(iov_r)) { |
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rc = PTR_ERR(iov_r); |
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goto free_iov_l; |
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} |
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rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); |
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if (iov_r != iovstack_r) |
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kfree(iov_r); |
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free_iov_l: |
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kfree(iov_l); |
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return rc; |
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} |
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SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, |
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unsigned long, liovcnt, const struct iovec __user *, rvec, |
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unsigned long, riovcnt, unsigned long, flags) |
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{ |
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return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0); |
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} |
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SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, |
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const struct iovec __user *, lvec, |
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unsigned long, liovcnt, const struct iovec __user *, rvec, |
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unsigned long, riovcnt, unsigned long, flags) |
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{ |
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return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1); |
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}
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