/*
* linux/mm/process_vm_access.c
*
* Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/mm.h>
#include <linux/uio.h>
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#ifdef CONFIG_COMPAT
#include <linux/compat.h>
#endif
/**
* process_vm_rw_pages - read/write pages from task specified
* @pages: array of pointers to pages we want to copy
* @start_offset: offset in page to start copying from/to
* @len: number of bytes to copy
* @iter: where to copy to/from locally
* @vm_write: 0 means copy from, 1 means copy to
* Returns 0 on success, error code otherwise
*/
static int process_vm_rw_pages(struct page **pages,
unsigned offset,
size_t len,
struct iov_iter *iter,
int vm_write)
{
/* Do the copy for each page */
while (len && iov_iter_count(iter)) {
struct page *page = *pages++;
size_t copy = PAGE_SIZE - offset;
size_t copied;
if (copy > len)
copy = len;
if (vm_write) {
copied = copy_page_from_iter(page, offset, copy, iter);
set_page_dirty_lock(page);
} else {
copied = copy_page_to_iter(page, offset, copy, iter);
}
len -= copied;
if (copied < copy && iov_iter_count(iter))
return -EFAULT;
offset = 0;
}
return 0;
}
/* Maximum number of pages kmalloc'd to hold struct page's during copy */
#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
/**
* process_vm_rw_single_vec - read/write pages from task specified
* @addr: start memory address of target process
* @len: size of area to copy to/from
* @iter: where to copy to/from locally
* @process_pages: struct pages area that can store at least
* nr_pages_to_copy struct page pointers
* @mm: mm for task
* @task: task to read/write from
* @vm_write: 0 means copy from, 1 means copy to
* Returns 0 on success or on failure error code
*/
static int process_vm_rw_single_vec(unsigned long addr,
unsigned long len,
struct iov_iter *iter,
struct page **process_pages,
struct mm_struct *mm,
struct task_struct *task,
int vm_write)
{
unsigned long pa = addr & PAGE_MASK;
unsigned long start_offset = addr - pa;
unsigned long nr_pages;
ssize_t rc = 0;
unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
/ sizeof(struct pages *);
/* Work out address and page range required */
if (len == 0)
return 0;
nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
while (!rc && nr_pages && iov_iter_count(iter)) {
int pages = min(nr_pages, max_pages_per_loop);
size_t bytes;
/* Get the pages we're interested in */
down_read(&mm->mmap_sem);
pages = get_user_pages(task, mm, pa, pages,
vm_write, 0, process_pages, NULL);
up_read(&mm->mmap_sem);
if (pages <= 0)
return -EFAULT;
bytes = pages * PAGE_SIZE - start_offset;
if (bytes > len)
bytes = len;
rc = process_vm_rw_pages(process_pages,
start_offset, bytes, iter,
vm_write);
len -= bytes;
start_offset = 0;
nr_pages -= pages;
pa += pages * PAGE_SIZE;
while (pages)
put_page(process_pages[--pages]);
}
return rc;
}
/* Maximum number of entries for process pages array
which lives on stack */
#define PVM_MAX_PP_ARRAY_COUNT 16
/**
* process_vm_rw_core - core of reading/writing pages from task specified
* @pid: PID of process to read/write from/to
* @iter: where to copy to/from locally
* @rvec: iovec array specifying where to copy to/from in the other process
* @riovcnt: size of rvec array
* @flags: currently unused
* @vm_write: 0 if reading from other process, 1 if writing to other process
* Returns the number of bytes read/written or error code. May
* return less bytes than expected if an error occurs during the copying
* process.
*/
static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
const struct iovec *rvec,
unsigned long riovcnt,
unsigned long flags, int vm_write)
{
struct task_struct *task;
struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
struct page **process_pages = pp_stack;
struct mm_struct *mm;
unsigned long i;
ssize_t rc = 0;
unsigned long nr_pages = 0;
unsigned long nr_pages_iov;
ssize_t iov_len;
size_t total_len = iov_iter_count(iter);
/*
* Work out how many pages of struct pages we're going to need
* when eventually calling get_user_pages
*/
for (i = 0; i < riovcnt; i++) {
iov_len = rvec[i].iov_len;
if (iov_len > 0) {
nr_pages_iov = ((unsigned long)rvec[i].iov_base
+ iov_len)
/ PAGE_SIZE - (unsigned long)rvec[i].iov_base
/ PAGE_SIZE + 1;
nr_pages = max(nr_pages, nr_pages_iov);
}
}
if (nr_pages == 0)
return 0;
if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
/* For reliability don't try to kmalloc more than
2 pages worth */
process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
sizeof(struct pages *)*nr_pages),
GFP_KERNEL);
if (!process_pages)
return -ENOMEM;
}
/* Get process information */
rcu_read_lock();
task = find_task_by_vpid(pid);
if (task)
get_task_struct(task);
rcu_read_unlock();
if (!task) {
rc = -ESRCH;
goto free_proc_pages;
}
mm = mm_access(task, PTRACE_MODE_ATTACH);
if (!mm || IS_ERR(mm)) {
rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
/*
* Explicitly map EACCES to EPERM as EPERM is a more a
* appropriate error code for process_vw_readv/writev
*/
if (rc == -EACCES)
rc = -EPERM;
goto put_task_struct;
}
for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
rc = process_vm_rw_single_vec(
(unsigned long)rvec[i].iov_base, rvec[i].iov_len,
iter, process_pages, mm, task, vm_write);
/* copied = space before - space after */
total_len -= iov_iter_count(iter);
/* If we have managed to copy any data at all then
we return the number of bytes copied. Otherwise
we return the error code */
if (total_len)
rc = total_len;
mmput(mm);
put_task_struct:
put_task_struct(task);
free_proc_pages:
if (process_pages != pp_stack)
kfree(process_pages);
return rc;
}
/**
* process_vm_rw - check iovecs before calling core routine
* @pid: PID of process to read/write from/to
* @lvec: iovec array specifying where to copy to/from locally
* @liovcnt: size of lvec array
* @rvec: iovec array specifying where to copy to/from in the other process
* @riovcnt: size of rvec array
* @flags: currently unused
* @vm_write: 0 if reading from other process, 1 if writing to other process
* Returns the number of bytes read/written or error code. May
* return less bytes than expected if an error occurs during the copying
* process.
*/
static ssize_t process_vm_rw(pid_t pid,
const struct iovec __user *lvec,
unsigned long liovcnt,
const struct iovec __user *rvec,
unsigned long riovcnt,
unsigned long flags, int vm_write)
{
struct iovec iovstack_l[UIO_FASTIOV];
struct iovec iovstack_r[UIO_FASTIOV];
struct iovec *iov_l = iovstack_l;
struct iovec *iov_r = iovstack_r;
struct iov_iter iter;
ssize_t rc;
if (flags != 0)
return -EINVAL;
/* Check iovecs */
if (vm_write)
rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
iovstack_l, &iov_l);
else
rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
iovstack_l, &iov_l);
if (rc <= 0)
goto free_iovecs;
iov_iter_init(&iter, vm_write ? WRITE : READ, iov_l, liovcnt, rc);
rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
iovstack_r, &iov_r);
if (rc <= 0)
goto free_iovecs;
rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
free_iovecs:
if (iov_r != iovstack_r)
kfree(iov_r);
if (iov_l != iovstack_l)
kfree(iov_l);
retur
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