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Christopher Yeohfcf63402011-10-31 17:06:39 -07001/*
2 * linux/mm/process_vm_access.c
3 *
4 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/mm.h>
13#include <linux/uio.h>
14#include <linux/sched.h>
15#include <linux/highmem.h>
16#include <linux/ptrace.h>
17#include <linux/slab.h>
18#include <linux/syscalls.h>
19
20#ifdef CONFIG_COMPAT
21#include <linux/compat.h>
22#endif
23
24/**
25 * process_vm_rw_pages - read/write pages from task specified
Al Viro4bafbec2014-02-05 13:25:32 -050026 * @pages: array of pointers to pages we want to copy
Christopher Yeohfcf63402011-10-31 17:06:39 -070027 * @start_offset: offset in page to start copying from/to
28 * @len: number of bytes to copy
Al Viro4bafbec2014-02-05 13:25:32 -050029 * @iter: where to copy to/from locally
Christopher Yeohfcf63402011-10-31 17:06:39 -070030 * @vm_write: 0 means copy from, 1 means copy to
Christopher Yeohfcf63402011-10-31 17:06:39 -070031 * Returns 0 on success, error code otherwise
32 */
Al Viro70eca122014-02-05 12:44:24 -050033static int process_vm_rw_pages(struct page **pages,
34 unsigned offset,
Al Viroe21345f2014-02-05 12:55:11 -050035 size_t len,
Al Viro9f78bdf2014-02-05 11:51:53 -050036 struct iov_iter *iter,
Al Viro9acc1a02014-02-05 13:15:28 -050037 int vm_write)
Christopher Yeohfcf63402011-10-31 17:06:39 -070038{
Christopher Yeohfcf63402011-10-31 17:06:39 -070039 /* Do the copy for each page */
Al Viro9acc1a02014-02-05 13:15:28 -050040 while (len && iov_iter_count(iter)) {
Al Viro70eca122014-02-05 12:44:24 -050041 struct page *page = *pages++;
Al Viroe21345f2014-02-05 12:55:11 -050042 size_t copy = PAGE_SIZE - offset;
Al Viro70eca122014-02-05 12:44:24 -050043 size_t copied;
Christopher Yeohfcf63402011-10-31 17:06:39 -070044
Al Viroe21345f2014-02-05 12:55:11 -050045 if (copy > len)
46 copy = len;
Christopher Yeohfcf63402011-10-31 17:06:39 -070047
Al Viro240f3902014-02-05 12:14:11 -050048 if (vm_write) {
Al Viro70eca122014-02-05 12:44:24 -050049 if (copy > iov_iter_count(iter))
50 copy = iov_iter_count(iter);
51 copied = iov_iter_copy_from_user(page, iter,
52 offset, copy);
53 iov_iter_advance(iter, copied);
Al Viro240f3902014-02-05 12:14:11 -050054 set_page_dirty_lock(page);
Christopher Yeohfcf63402011-10-31 17:06:39 -070055 } else {
Al Viro70eca122014-02-05 12:44:24 -050056 copied = copy_page_to_iter(page, offset, copy, iter);
Christopher Yeohfcf63402011-10-31 17:06:39 -070057 }
Al Viro70eca122014-02-05 12:44:24 -050058 len -= copied;
59 if (copied < copy && iov_iter_count(iter))
60 return -EFAULT;
61 offset = 0;
Christopher Yeohfcf63402011-10-31 17:06:39 -070062 }
Al Viro70eca122014-02-05 12:44:24 -050063 return 0;
Christopher Yeohfcf63402011-10-31 17:06:39 -070064}
65
66/* Maximum number of pages kmalloc'd to hold struct page's during copy */
67#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
68
69/**
70 * process_vm_rw_single_vec - read/write pages from task specified
71 * @addr: start memory address of target process
72 * @len: size of area to copy to/from
Al Viro4bafbec2014-02-05 13:25:32 -050073 * @iter: where to copy to/from locally
Christopher Yeohfcf63402011-10-31 17:06:39 -070074 * @process_pages: struct pages area that can store at least
75 * nr_pages_to_copy struct page pointers
76 * @mm: mm for task
77 * @task: task to read/write from
78 * @vm_write: 0 means copy from, 1 means copy to
Christopher Yeohfcf63402011-10-31 17:06:39 -070079 * Returns 0 on success or on failure error code
80 */
81static int process_vm_rw_single_vec(unsigned long addr,
82 unsigned long len,
Al Viro9f78bdf2014-02-05 11:51:53 -050083 struct iov_iter *iter,
Christopher Yeohfcf63402011-10-31 17:06:39 -070084 struct page **process_pages,
85 struct mm_struct *mm,
86 struct task_struct *task,
Al Viro9acc1a02014-02-05 13:15:28 -050087 int vm_write)
Christopher Yeohfcf63402011-10-31 17:06:39 -070088{
89 unsigned long pa = addr & PAGE_MASK;
90 unsigned long start_offset = addr - pa;
91 unsigned long nr_pages;
Christopher Yeohfcf63402011-10-31 17:06:39 -070092 ssize_t rc = 0;
Christopher Yeohfcf63402011-10-31 17:06:39 -070093 unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
94 / sizeof(struct pages *);
95
Christopher Yeohfcf63402011-10-31 17:06:39 -070096 /* Work out address and page range required */
97 if (len == 0)
98 return 0;
99 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
100
Al Viro4bafbec2014-02-05 13:25:32 -0500101 while (!rc && nr_pages && iov_iter_count(iter)) {
102 int pages = min(nr_pages, max_pages_per_loop);
103 size_t bytes;
Christopher Yeohfcf63402011-10-31 17:06:39 -0700104
Al Viro70eca122014-02-05 12:44:24 -0500105 /* Get the pages we're interested in */
106 down_read(&mm->mmap_sem);
Al Viro4bafbec2014-02-05 13:25:32 -0500107 pages = get_user_pages(task, mm, pa, pages,
108 vm_write, 0, process_pages, NULL);
Al Viro70eca122014-02-05 12:44:24 -0500109 up_read(&mm->mmap_sem);
110
Al Viro4bafbec2014-02-05 13:25:32 -0500111 if (pages <= 0)
Al Viro70eca122014-02-05 12:44:24 -0500112 return -EFAULT;
113
Al Viro4bafbec2014-02-05 13:25:32 -0500114 bytes = pages * PAGE_SIZE - start_offset;
115 if (bytes > len)
116 bytes = len;
Al Viroe21345f2014-02-05 12:55:11 -0500117
Al Viro70eca122014-02-05 12:44:24 -0500118 rc = process_vm_rw_pages(process_pages,
Al Viro4bafbec2014-02-05 13:25:32 -0500119 start_offset, bytes, iter,
Al Viro9acc1a02014-02-05 13:15:28 -0500120 vm_write);
Al Viro4bafbec2014-02-05 13:25:32 -0500121 len -= bytes;
Christopher Yeohfcf63402011-10-31 17:06:39 -0700122 start_offset = 0;
Al Viro4bafbec2014-02-05 13:25:32 -0500123 nr_pages -= pages;
124 pa += pages * PAGE_SIZE;
125 while (pages)
126 put_page(process_pages[--pages]);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700127 }
128
129 return rc;
130}
131
132/* Maximum number of entries for process pages array
133 which lives on stack */
134#define PVM_MAX_PP_ARRAY_COUNT 16
135
136/**
137 * process_vm_rw_core - core of reading/writing pages from task specified
138 * @pid: PID of process to read/write from/to
Al Viro4bafbec2014-02-05 13:25:32 -0500139 * @iter: where to copy to/from locally
Christopher Yeohfcf63402011-10-31 17:06:39 -0700140 * @rvec: iovec array specifying where to copy to/from in the other process
141 * @riovcnt: size of rvec array
142 * @flags: currently unused
143 * @vm_write: 0 if reading from other process, 1 if writing to other process
144 * Returns the number of bytes read/written or error code. May
145 * return less bytes than expected if an error occurs during the copying
146 * process.
147 */
Al Viro9f78bdf2014-02-05 11:51:53 -0500148static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
Christopher Yeohfcf63402011-10-31 17:06:39 -0700149 const struct iovec *rvec,
150 unsigned long riovcnt,
151 unsigned long flags, int vm_write)
152{
153 struct task_struct *task;
154 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
155 struct page **process_pages = pp_stack;
156 struct mm_struct *mm;
157 unsigned long i;
158 ssize_t rc = 0;
Christopher Yeohfcf63402011-10-31 17:06:39 -0700159 unsigned long nr_pages = 0;
160 unsigned long nr_pages_iov;
Christopher Yeohfcf63402011-10-31 17:06:39 -0700161 ssize_t iov_len;
Al Viro9acc1a02014-02-05 13:15:28 -0500162 size_t total_len = iov_iter_count(iter);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700163
164 /*
165 * Work out how many pages of struct pages we're going to need
166 * when eventually calling get_user_pages
167 */
168 for (i = 0; i < riovcnt; i++) {
169 iov_len = rvec[i].iov_len;
170 if (iov_len > 0) {
171 nr_pages_iov = ((unsigned long)rvec[i].iov_base
172 + iov_len)
173 / PAGE_SIZE - (unsigned long)rvec[i].iov_base
174 / PAGE_SIZE + 1;
175 nr_pages = max(nr_pages, nr_pages_iov);
176 }
177 }
178
179 if (nr_pages == 0)
180 return 0;
181
182 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
183 /* For reliability don't try to kmalloc more than
184 2 pages worth */
185 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
186 sizeof(struct pages *)*nr_pages),
187 GFP_KERNEL);
188
189 if (!process_pages)
190 return -ENOMEM;
191 }
192
193 /* Get process information */
194 rcu_read_lock();
195 task = find_task_by_vpid(pid);
196 if (task)
197 get_task_struct(task);
198 rcu_read_unlock();
199 if (!task) {
200 rc = -ESRCH;
201 goto free_proc_pages;
202 }
203
Christopher Yeoh8cdb8782012-02-02 11:34:09 +1030204 mm = mm_access(task, PTRACE_MODE_ATTACH);
205 if (!mm || IS_ERR(mm)) {
206 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
207 /*
208 * Explicitly map EACCES to EPERM as EPERM is a more a
209 * appropriate error code for process_vw_readv/writev
210 */
211 if (rc == -EACCES)
212 rc = -EPERM;
Christopher Yeohfcf63402011-10-31 17:06:39 -0700213 goto put_task_struct;
214 }
Christopher Yeohfcf63402011-10-31 17:06:39 -0700215
Al Viro9acc1a02014-02-05 13:15:28 -0500216 for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
Christopher Yeohfcf63402011-10-31 17:06:39 -0700217 rc = process_vm_rw_single_vec(
218 (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
Al Viro9acc1a02014-02-05 13:15:28 -0500219 iter, process_pages, mm, task, vm_write);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700220
Al Viro9acc1a02014-02-05 13:15:28 -0500221 /* copied = space before - space after */
222 total_len -= iov_iter_count(iter);
223
224 /* If we have managed to copy any data at all then
225 we return the number of bytes copied. Otherwise
226 we return the error code */
227 if (total_len)
228 rc = total_len;
229
Christopher Yeohfcf63402011-10-31 17:06:39 -0700230 mmput(mm);
231
232put_task_struct:
233 put_task_struct(task);
234
235free_proc_pages:
236 if (process_pages != pp_stack)
237 kfree(process_pages);
238 return rc;
239}
240
241/**
242 * process_vm_rw - check iovecs before calling core routine
243 * @pid: PID of process to read/write from/to
244 * @lvec: iovec array specifying where to copy to/from locally
245 * @liovcnt: size of lvec array
246 * @rvec: iovec array specifying where to copy to/from in the other process
247 * @riovcnt: size of rvec array
248 * @flags: currently unused
249 * @vm_write: 0 if reading from other process, 1 if writing to other process
250 * Returns the number of bytes read/written or error code. May
251 * return less bytes than expected if an error occurs during the copying
252 * process.
253 */
254static ssize_t process_vm_rw(pid_t pid,
255 const struct iovec __user *lvec,
256 unsigned long liovcnt,
257 const struct iovec __user *rvec,
258 unsigned long riovcnt,
259 unsigned long flags, int vm_write)
260{
261 struct iovec iovstack_l[UIO_FASTIOV];
262 struct iovec iovstack_r[UIO_FASTIOV];
263 struct iovec *iov_l = iovstack_l;
264 struct iovec *iov_r = iovstack_r;
Al Viro9f78bdf2014-02-05 11:51:53 -0500265 struct iov_iter iter;
Christopher Yeohfcf63402011-10-31 17:06:39 -0700266 ssize_t rc;
267
268 if (flags != 0)
269 return -EINVAL;
270
271 /* Check iovecs */
272 if (vm_write)
273 rc = rw_copy_check_uvector(WRITE, lvec, liovcnt, UIO_FASTIOV,
Christopher Yeohac34ebb2012-05-31 16:26:42 -0700274 iovstack_l, &iov_l);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700275 else
276 rc = rw_copy_check_uvector(READ, lvec, liovcnt, UIO_FASTIOV,
Christopher Yeohac34ebb2012-05-31 16:26:42 -0700277 iovstack_l, &iov_l);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700278 if (rc <= 0)
279 goto free_iovecs;
280
Al Viro9f78bdf2014-02-05 11:51:53 -0500281 iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
282
Christopher Yeohac34ebb2012-05-31 16:26:42 -0700283 rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
284 iovstack_r, &iov_r);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700285 if (rc <= 0)
286 goto free_iovecs;
287
Al Viro9f78bdf2014-02-05 11:51:53 -0500288 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700289
290free_iovecs:
291 if (iov_r != iovstack_r)
292 kfree(iov_r);
293 if (iov_l != iovstack_l)
294 kfree(iov_l);
295
296 return rc;
297}
298
299SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
300 unsigned long, liovcnt, const struct iovec __user *, rvec,
301 unsigned long, riovcnt, unsigned long, flags)
302{
303 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
304}
305
306SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
307 const struct iovec __user *, lvec,
308 unsigned long, liovcnt, const struct iovec __user *, rvec,
309 unsigned long, riovcnt, unsigned long, flags)
310{
311 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
312}
313
314#ifdef CONFIG_COMPAT
315
Rashika Kheria2eb2e142014-04-03 14:48:04 -0700316static ssize_t
Christopher Yeohfcf63402011-10-31 17:06:39 -0700317compat_process_vm_rw(compat_pid_t pid,
318 const struct compat_iovec __user *lvec,
319 unsigned long liovcnt,
320 const struct compat_iovec __user *rvec,
321 unsigned long riovcnt,
322 unsigned long flags, int vm_write)
323{
324 struct iovec iovstack_l[UIO_FASTIOV];
325 struct iovec iovstack_r[UIO_FASTIOV];
326 struct iovec *iov_l = iovstack_l;
327 struct iovec *iov_r = iovstack_r;
Al Viro9f78bdf2014-02-05 11:51:53 -0500328 struct iov_iter iter;
Christopher Yeohfcf63402011-10-31 17:06:39 -0700329 ssize_t rc = -EFAULT;
330
331 if (flags != 0)
332 return -EINVAL;
333
Christopher Yeohfcf63402011-10-31 17:06:39 -0700334 if (vm_write)
335 rc = compat_rw_copy_check_uvector(WRITE, lvec, liovcnt,
336 UIO_FASTIOV, iovstack_l,
Christopher Yeohac34ebb2012-05-31 16:26:42 -0700337 &iov_l);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700338 else
339 rc = compat_rw_copy_check_uvector(READ, lvec, liovcnt,
340 UIO_FASTIOV, iovstack_l,
Christopher Yeohac34ebb2012-05-31 16:26:42 -0700341 &iov_l);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700342 if (rc <= 0)
343 goto free_iovecs;
Al Viro9f78bdf2014-02-05 11:51:53 -0500344 iov_iter_init(&iter, iov_l, liovcnt, rc, 0);
Christopher Yeohac34ebb2012-05-31 16:26:42 -0700345 rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
Christopher Yeohfcf63402011-10-31 17:06:39 -0700346 UIO_FASTIOV, iovstack_r,
Christopher Yeohac34ebb2012-05-31 16:26:42 -0700347 &iov_r);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700348 if (rc <= 0)
349 goto free_iovecs;
350
Al Viro9f78bdf2014-02-05 11:51:53 -0500351 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700352
353free_iovecs:
354 if (iov_r != iovstack_r)
355 kfree(iov_r);
356 if (iov_l != iovstack_l)
357 kfree(iov_l);
Christopher Yeohfcf63402011-10-31 17:06:39 -0700358 return rc;
359}
360
Heiko Carstens2f2728f2014-03-04 17:18:23 +0100361COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid,
362 const struct compat_iovec __user *, lvec,
363 compat_ulong_t, liovcnt,
364 const struct compat_iovec __user *, rvec,
365 compat_ulong_t, riovcnt,
366 compat_ulong_t, flags)
Christopher Yeohfcf63402011-10-31 17:06:39 -0700367{
368 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
369 riovcnt, flags, 0);
370}
371
Heiko Carstens2f2728f2014-03-04 17:18:23 +0100372COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid,
373 const struct compat_iovec __user *, lvec,
374 compat_ulong_t, liovcnt,
375 const struct compat_iovec __user *, rvec,
376 compat_ulong_t, riovcnt,
377 compat_ulong_t, flags)
Christopher Yeohfcf63402011-10-31 17:06:39 -0700378{
379 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
380 riovcnt, flags, 1);
381}
382
383#endif