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![Christopher Yeoh](/assets/img/avatar_default.png)
A cleanup of rw_copy_check_uvector and compat_rw_copy_check_uvector after changes made to support CMA in an earlier patch. Rather than having an additional check_access parameter to these functions, the first paramater type is overloaded to allow the caller to specify CHECK_IOVEC_ONLY which means check that the contents of the iovec are valid, but do not check the memory that they point to. This is used by process_vm_readv/writev where we need to validate that a iovec passed to the syscall is valid but do not want to check the memory that it points to at this point because it refers to an address space in another process. Signed-off-by: Chris Yeoh <yeohc@au1.ibm.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
491 lines
13 KiB
C
491 lines
13 KiB
C
/*
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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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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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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/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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#ifdef CONFIG_COMPAT
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#include <linux/compat.h>
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#endif
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/**
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* process_vm_rw_pages - read/write pages from task specified
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* @task: task to read/write from
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* @mm: mm for task
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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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* @pa: address of page in task to start copying from/to
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* @start_offset: offset in page to start copying from/to
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* @len: number of bytes to copy
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* @lvec: iovec array specifying where to copy to/from
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* @lvec_cnt: number of elements in iovec array
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* @lvec_current: index in iovec array we are up to
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* @lvec_offset: offset in bytes from current iovec iov_base we are up to
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* @vm_write: 0 means copy from, 1 means copy to
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* @nr_pages_to_copy: number of pages to copy
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* @bytes_copied: returns number of bytes successfully copied
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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 task_struct *task,
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struct mm_struct *mm,
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struct page **process_pages,
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unsigned long pa,
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unsigned long start_offset,
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unsigned long len,
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const struct iovec *lvec,
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unsigned long lvec_cnt,
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unsigned long *lvec_current,
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size_t *lvec_offset,
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int vm_write,
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unsigned int nr_pages_to_copy,
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ssize_t *bytes_copied)
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{
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int pages_pinned;
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void *target_kaddr;
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int pgs_copied = 0;
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int j;
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int ret;
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ssize_t bytes_to_copy;
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ssize_t rc = 0;
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*bytes_copied = 0;
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/* Get the pages we're interested in */
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down_read(&mm->mmap_sem);
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pages_pinned = get_user_pages(task, mm, pa,
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nr_pages_to_copy,
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vm_write, 0, process_pages, NULL);
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up_read(&mm->mmap_sem);
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if (pages_pinned != nr_pages_to_copy) {
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rc = -EFAULT;
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goto end;
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}
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/* Do the copy for each page */
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for (pgs_copied = 0;
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(pgs_copied < nr_pages_to_copy) && (*lvec_current < lvec_cnt);
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pgs_copied++) {
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/* Make sure we have a non zero length iovec */
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while (*lvec_current < lvec_cnt
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&& lvec[*lvec_current].iov_len == 0)
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(*lvec_current)++;
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if (*lvec_current == lvec_cnt)
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break;
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/*
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* Will copy smallest of:
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* - bytes remaining in page
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* - bytes remaining in destination iovec
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*/
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bytes_to_copy = min_t(ssize_t, PAGE_SIZE - start_offset,
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len - *bytes_copied);
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bytes_to_copy = min_t(ssize_t, bytes_to_copy,
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lvec[*lvec_current].iov_len
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- *lvec_offset);
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target_kaddr = kmap(process_pages[pgs_copied]) + start_offset;
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if (vm_write)
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ret = copy_from_user(target_kaddr,
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lvec[*lvec_current].iov_base
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+ *lvec_offset,
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bytes_to_copy);
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else
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ret = copy_to_user(lvec[*lvec_current].iov_base
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+ *lvec_offset,
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target_kaddr, bytes_to_copy);
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kunmap(process_pages[pgs_copied]);
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if (ret) {
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*bytes_copied += bytes_to_copy - ret;
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pgs_copied++;
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rc = -EFAULT;
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goto end;
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}
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*bytes_copied += bytes_to_copy;
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*lvec_offset += bytes_to_copy;
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if (*lvec_offset == lvec[*lvec_current].iov_len) {
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/*
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* Need to copy remaining part of page into the
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* next iovec if there are any bytes left in page
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*/
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(*lvec_current)++;
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*lvec_offset = 0;
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start_offset = (start_offset + bytes_to_copy)
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% PAGE_SIZE;
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if (start_offset)
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pgs_copied--;
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} else {
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start_offset = 0;
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}
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}
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end:
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if (vm_write) {
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for (j = 0; j < pages_pinned; j++) {
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if (j < pgs_copied)
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set_page_dirty_lock(process_pages[j]);
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put_page(process_pages[j]);
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}
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} else {
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for (j = 0; j < pages_pinned; j++)
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put_page(process_pages[j]);
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}
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return rc;
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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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* @lvec: iovec array specifying where to copy to/from locally
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* @lvec_cnt: number of elements in iovec array
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* @lvec_current: index in iovec array we are up to
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* @lvec_offset: offset in bytes from current iovec iov_base we are up to
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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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* @bytes_copied: returns number of bytes successfully copied
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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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const struct iovec *lvec,
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unsigned long lvec_cnt,
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unsigned long *lvec_current,
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size_t *lvec_offset,
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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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ssize_t *bytes_copied)
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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 bytes_copied_loop;
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ssize_t rc = 0;
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unsigned long nr_pages_copied = 0;
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unsigned long nr_pages_to_copy;
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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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*bytes_copied = 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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while ((nr_pages_copied < nr_pages) && (*lvec_current < lvec_cnt)) {
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nr_pages_to_copy = min(nr_pages - nr_pages_copied,
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max_pages_per_loop);
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rc = process_vm_rw_pages(task, mm, process_pages, pa,
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start_offset, len,
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lvec, lvec_cnt,
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lvec_current, lvec_offset,
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vm_write, nr_pages_to_copy,
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&bytes_copied_loop);
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start_offset = 0;
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*bytes_copied += bytes_copied_loop;
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if (rc < 0) {
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return rc;
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} else {
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len -= bytes_copied_loop;
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nr_pages_copied += nr_pages_to_copy;
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pa += nr_pages_to_copy * PAGE_SIZE;
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}
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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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* @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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* 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, const struct iovec *lvec,
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unsigned long liovcnt,
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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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ssize_t bytes_copied_loop;
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ssize_t bytes_copied = 0;
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unsigned long nr_pages = 0;
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unsigned long nr_pages_iov;
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unsigned long iov_l_curr_idx = 0;
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size_t iov_l_curr_offset = 0;
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ssize_t iov_len;
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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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rcu_read_lock();
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task = find_task_by_vpid(pid);
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if (task)
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get_task_struct(task);
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rcu_read_unlock();
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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);
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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 a
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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_l_curr_idx < liovcnt; 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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lvec, liovcnt, &iov_l_curr_idx, &iov_l_curr_offset,
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process_pages, mm, task, vm_write, &bytes_copied_loop);
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bytes_copied += bytes_copied_loop;
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if (rc != 0) {
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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 (bytes_copied)
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rc = bytes_copied;
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goto put_mm;
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}
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}
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rc = bytes_copied;
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put_mm:
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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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* 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 = iovstack_r;
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ssize_t rc;
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if (flags != 0)
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return -EINVAL;
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/* Check iovecs */
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if (vm_write)
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rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
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iovstack_l, &iov_l);
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else
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rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
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iovstack_l, &iov_l);
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if (rc <= 0)
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goto free_iovecs;
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rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
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iovstack_r, &iov_r);
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if (rc <= 0)
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goto free_iovecs;
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rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
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vm_write);
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free_iovecs:
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if (iov_r != iovstack_r)
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kfree(iov_r);
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if (iov_l != iovstack_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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#ifdef CONFIG_COMPAT
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asmlinkage ssize_t
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compat_process_vm_rw(compat_pid_t pid,
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const struct compat_iovec __user *lvec,
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unsigned long liovcnt,
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const struct compat_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 = iovstack_r;
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ssize_t rc = -EFAULT;
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if (flags != 0)
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return -EINVAL;
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if (!access_ok(VERIFY_READ, lvec, liovcnt * sizeof(*lvec)))
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goto out;
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if (!access_ok(VERIFY_READ, rvec, riovcnt * sizeof(*rvec)))
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goto out;
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if (vm_write)
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rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
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UIO_FASTIOV, iovstack_l,
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&iov_l);
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else
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rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
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UIO_FASTIOV, iovstack_l,
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&iov_l);
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if (rc <= 0)
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goto free_iovecs;
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rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
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UIO_FASTIOV, iovstack_r,
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&iov_r);
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if (rc <= 0)
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goto free_iovecs;
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rc = process_vm_rw_core(pid, iov_l, liovcnt, iov_r, riovcnt, flags,
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vm_write);
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free_iovecs:
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if (iov_r != iovstack_r)
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kfree(iov_r);
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if (iov_l != iovstack_l)
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kfree(iov_l);
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out:
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return rc;
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}
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asmlinkage ssize_t
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compat_sys_process_vm_readv(compat_pid_t pid,
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const struct compat_iovec __user *lvec,
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unsigned long liovcnt,
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const struct compat_iovec __user *rvec,
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unsigned long riovcnt,
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unsigned long flags)
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{
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return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
|
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riovcnt, flags, 0);
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|
}
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|
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asmlinkage ssize_t
|
|
compat_sys_process_vm_writev(compat_pid_t pid,
|
|
const struct compat_iovec __user *lvec,
|
|
unsigned long liovcnt,
|
|
const struct compat_iovec __user *rvec,
|
|
unsigned long riovcnt,
|
|
unsigned long flags)
|
|
{
|
|
return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
|
|
riovcnt, flags, 1);
|
|
}
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|
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#endif
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