305 lines
8.2 KiB
C
305 lines
8.2 KiB
C
// 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 <cyeoh@au1.ibm.com>, 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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