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fcf63409 CY |
1 | /* |
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 | |
4bafbec7 | 26 | * @pages: array of pointers to pages we want to copy |
fcf63409 CY |
27 | * @start_offset: offset in page to start copying from/to |
28 | * @len: number of bytes to copy | |
4bafbec7 | 29 | * @iter: where to copy to/from locally |
fcf63409 | 30 | * @vm_write: 0 means copy from, 1 means copy to |
fcf63409 CY |
31 | * Returns 0 on success, error code otherwise |
32 | */ | |
70eca12d AV |
33 | static int process_vm_rw_pages(struct page **pages, |
34 | unsigned offset, | |
e21345f9 | 35 | size_t len, |
9f78bdfa | 36 | struct iov_iter *iter, |
9acc1a0f | 37 | int vm_write) |
fcf63409 | 38 | { |
fcf63409 | 39 | /* Do the copy for each page */ |
9acc1a0f | 40 | while (len && iov_iter_count(iter)) { |
70eca12d | 41 | struct page *page = *pages++; |
e21345f9 | 42 | size_t copy = PAGE_SIZE - offset; |
70eca12d | 43 | size_t copied; |
240f3905 | 44 | |
e21345f9 AV |
45 | if (copy > len) |
46 | copy = len; | |
47 | ||
240f3905 | 48 | if (vm_write) { |
e7c24607 | 49 | copied = copy_page_from_iter(page, offset, copy, iter); |
240f3905 | 50 | set_page_dirty_lock(page); |
fcf63409 | 51 | } else { |
70eca12d | 52 | copied = copy_page_to_iter(page, offset, copy, iter); |
fcf63409 | 53 | } |
70eca12d AV |
54 | len -= copied; |
55 | if (copied < copy && iov_iter_count(iter)) | |
56 | return -EFAULT; | |
57 | offset = 0; | |
fcf63409 | 58 | } |
70eca12d | 59 | return 0; |
fcf63409 CY |
60 | } |
61 | ||
62 | /* Maximum number of pages kmalloc'd to hold struct page's during copy */ | |
63 | #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2) | |
64 | ||
65 | /** | |
66 | * process_vm_rw_single_vec - read/write pages from task specified | |
67 | * @addr: start memory address of target process | |
68 | * @len: size of area to copy to/from | |
4bafbec7 | 69 | * @iter: where to copy to/from locally |
fcf63409 CY |
70 | * @process_pages: struct pages area that can store at least |
71 | * nr_pages_to_copy struct page pointers | |
72 | * @mm: mm for task | |
73 | * @task: task to read/write from | |
74 | * @vm_write: 0 means copy from, 1 means copy to | |
fcf63409 CY |
75 | * Returns 0 on success or on failure error code |
76 | */ | |
77 | static int process_vm_rw_single_vec(unsigned long addr, | |
78 | unsigned long len, | |
9f78bdfa | 79 | struct iov_iter *iter, |
fcf63409 CY |
80 | struct page **process_pages, |
81 | struct mm_struct *mm, | |
82 | struct task_struct *task, | |
9acc1a0f | 83 | int vm_write) |
fcf63409 CY |
84 | { |
85 | unsigned long pa = addr & PAGE_MASK; | |
86 | unsigned long start_offset = addr - pa; | |
87 | unsigned long nr_pages; | |
fcf63409 | 88 | ssize_t rc = 0; |
fcf63409 CY |
89 | unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES |
90 | / sizeof(struct pages *); | |
8b7457ef | 91 | unsigned int flags = 0; |
fcf63409 | 92 | |
fcf63409 CY |
93 | /* Work out address and page range required */ |
94 | if (len == 0) | |
95 | return 0; | |
96 | nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; | |
97 | ||
d4944b0e LS |
98 | if (vm_write) |
99 | flags |= FOLL_WRITE; | |
100 | ||
4bafbec7 AV |
101 | while (!rc && nr_pages && iov_iter_count(iter)) { |
102 | int pages = min(nr_pages, max_pages_per_loop); | |
8b7457ef | 103 | int locked = 1; |
4bafbec7 | 104 | size_t bytes; |
fcf63409 | 105 | |
1e987790 DH |
106 | /* |
107 | * Get the pages we're interested in. We must | |
8b7457ef | 108 | * access remotely because task/mm might not |
1e987790 DH |
109 | * current/current->mm |
110 | */ | |
8b7457ef LS |
111 | down_read(&mm->mmap_sem); |
112 | pages = get_user_pages_remote(task, mm, pa, pages, flags, | |
113 | process_pages, NULL, &locked); | |
114 | if (locked) | |
115 | up_read(&mm->mmap_sem); | |
4bafbec7 | 116 | if (pages <= 0) |
70eca12d AV |
117 | return -EFAULT; |
118 | ||
4bafbec7 AV |
119 | bytes = pages * PAGE_SIZE - start_offset; |
120 | if (bytes > len) | |
121 | bytes = len; | |
e21345f9 | 122 | |
70eca12d | 123 | rc = process_vm_rw_pages(process_pages, |
4bafbec7 | 124 | start_offset, bytes, iter, |
9acc1a0f | 125 | vm_write); |
4bafbec7 | 126 | len -= bytes; |
fcf63409 | 127 | start_offset = 0; |
4bafbec7 AV |
128 | nr_pages -= pages; |
129 | pa += pages * PAGE_SIZE; | |
130 | while (pages) | |
131 | put_page(process_pages[--pages]); | |
fcf63409 CY |
132 | } |
133 | ||
134 | return rc; | |
135 | } | |
136 | ||
137 | /* Maximum number of entries for process pages array | |
138 | which lives on stack */ | |
139 | #define PVM_MAX_PP_ARRAY_COUNT 16 | |
140 | ||
141 | /** | |
142 | * process_vm_rw_core - core of reading/writing pages from task specified | |
143 | * @pid: PID of process to read/write from/to | |
4bafbec7 | 144 | * @iter: where to copy to/from locally |
fcf63409 CY |
145 | * @rvec: iovec array specifying where to copy to/from in the other process |
146 | * @riovcnt: size of rvec array | |
147 | * @flags: currently unused | |
148 | * @vm_write: 0 if reading from other process, 1 if writing to other process | |
149 | * Returns the number of bytes read/written or error code. May | |
150 | * return less bytes than expected if an error occurs during the copying | |
151 | * process. | |
152 | */ | |
9f78bdfa | 153 | static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, |
fcf63409 CY |
154 | const struct iovec *rvec, |
155 | unsigned long riovcnt, | |
156 | unsigned long flags, int vm_write) | |
157 | { | |
158 | struct task_struct *task; | |
159 | struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; | |
160 | struct page **process_pages = pp_stack; | |
161 | struct mm_struct *mm; | |
162 | unsigned long i; | |
163 | ssize_t rc = 0; | |
fcf63409 CY |
164 | unsigned long nr_pages = 0; |
165 | unsigned long nr_pages_iov; | |
fcf63409 | 166 | ssize_t iov_len; |
9acc1a0f | 167 | size_t total_len = iov_iter_count(iter); |
fcf63409 CY |
168 | |
169 | /* | |
170 | * Work out how many pages of struct pages we're going to need | |
171 | * when eventually calling get_user_pages | |
172 | */ | |
173 | for (i = 0; i < riovcnt; i++) { | |
174 | iov_len = rvec[i].iov_len; | |
175 | if (iov_len > 0) { | |
176 | nr_pages_iov = ((unsigned long)rvec[i].iov_base | |
177 | + iov_len) | |
178 | / PAGE_SIZE - (unsigned long)rvec[i].iov_base | |
179 | / PAGE_SIZE + 1; | |
180 | nr_pages = max(nr_pages, nr_pages_iov); | |
181 | } | |
182 | } | |
183 | ||
184 | if (nr_pages == 0) | |
185 | return 0; | |
186 | ||
187 | if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { | |
188 | /* For reliability don't try to kmalloc more than | |
189 | 2 pages worth */ | |
190 | process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, | |
191 | sizeof(struct pages *)*nr_pages), | |
192 | GFP_KERNEL); | |
193 | ||
194 | if (!process_pages) | |
195 | return -ENOMEM; | |
196 | } | |
197 | ||
198 | /* Get process information */ | |
199 | rcu_read_lock(); | |
200 | task = find_task_by_vpid(pid); | |
201 | if (task) | |
202 | get_task_struct(task); | |
203 | rcu_read_unlock(); | |
204 | if (!task) { | |
205 | rc = -ESRCH; | |
206 | goto free_proc_pages; | |
207 | } | |
208 | ||
caaee623 | 209 | mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); |
8cdb878d CY |
210 | if (!mm || IS_ERR(mm)) { |
211 | rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; | |
212 | /* | |
213 | * Explicitly map EACCES to EPERM as EPERM is a more a | |
214 | * appropriate error code for process_vw_readv/writev | |
215 | */ | |
216 | if (rc == -EACCES) | |
217 | rc = -EPERM; | |
fcf63409 CY |
218 | goto put_task_struct; |
219 | } | |
220 | ||
9acc1a0f | 221 | for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++) |
fcf63409 CY |
222 | rc = process_vm_rw_single_vec( |
223 | (unsigned long)rvec[i].iov_base, rvec[i].iov_len, | |
9acc1a0f AV |
224 | iter, process_pages, mm, task, vm_write); |
225 | ||
226 | /* copied = space before - space after */ | |
227 | total_len -= iov_iter_count(iter); | |
228 | ||
229 | /* If we have managed to copy any data at all then | |
230 | we return the number of bytes copied. Otherwise | |
231 | we return the error code */ | |
232 | if (total_len) | |
233 | rc = total_len; | |
fcf63409 | 234 | |
fcf63409 CY |
235 | mmput(mm); |
236 | ||
237 | put_task_struct: | |
238 | put_task_struct(task); | |
239 | ||
240 | free_proc_pages: | |
241 | if (process_pages != pp_stack) | |
242 | kfree(process_pages); | |
243 | return rc; | |
244 | } | |
245 | ||
246 | /** | |
247 | * process_vm_rw - check iovecs before calling core routine | |
248 | * @pid: PID of process to read/write from/to | |
249 | * @lvec: iovec array specifying where to copy to/from locally | |
250 | * @liovcnt: size of lvec array | |
251 | * @rvec: iovec array specifying where to copy to/from in the other process | |
252 | * @riovcnt: size of rvec array | |
253 | * @flags: currently unused | |
254 | * @vm_write: 0 if reading from other process, 1 if writing to other process | |
255 | * Returns the number of bytes read/written or error code. May | |
256 | * return less bytes than expected if an error occurs during the copying | |
257 | * process. | |
258 | */ | |
259 | static ssize_t process_vm_rw(pid_t pid, | |
260 | const struct iovec __user *lvec, | |
261 | unsigned long liovcnt, | |
262 | const struct iovec __user *rvec, | |
263 | unsigned long riovcnt, | |
264 | unsigned long flags, int vm_write) | |
265 | { | |
266 | struct iovec iovstack_l[UIO_FASTIOV]; | |
267 | struct iovec iovstack_r[UIO_FASTIOV]; | |
268 | struct iovec *iov_l = iovstack_l; | |
269 | struct iovec *iov_r = iovstack_r; | |
9f78bdfa | 270 | struct iov_iter iter; |
fcf63409 | 271 | ssize_t rc; |
17d17e72 | 272 | int dir = vm_write ? WRITE : READ; |
fcf63409 CY |
273 | |
274 | if (flags != 0) | |
275 | return -EINVAL; | |
276 | ||
277 | /* Check iovecs */ | |
17d17e72 AV |
278 | rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); |
279 | if (rc < 0) | |
280 | return rc; | |
281 | if (!iov_iter_count(&iter)) | |
fcf63409 CY |
282 | goto free_iovecs; |
283 | ||
ac34ebb3 CY |
284 | rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV, |
285 | iovstack_r, &iov_r); | |
fcf63409 CY |
286 | if (rc <= 0) |
287 | goto free_iovecs; | |
288 | ||
9f78bdfa | 289 | rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); |
fcf63409 CY |
290 | |
291 | free_iovecs: | |
292 | if (iov_r != iovstack_r) | |
293 | kfree(iov_r); | |
17d17e72 | 294 | kfree(iov_l); |
fcf63409 CY |
295 | |
296 | return rc; | |
297 | } | |
298 | ||
299 | SYSCALL_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 | ||
306 | SYSCALL_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 | ||
2eb2e141 | 316 | static ssize_t |
fcf63409 CY |
317 | compat_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; | |
9f78bdfa | 328 | struct iov_iter iter; |
fcf63409 | 329 | ssize_t rc = -EFAULT; |
17d17e72 | 330 | int dir = vm_write ? WRITE : READ; |
fcf63409 CY |
331 | |
332 | if (flags != 0) | |
333 | return -EINVAL; | |
334 | ||
17d17e72 AV |
335 | rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); |
336 | if (rc < 0) | |
337 | return rc; | |
338 | if (!iov_iter_count(&iter)) | |
fcf63409 | 339 | goto free_iovecs; |
ac34ebb3 | 340 | rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, |
fcf63409 | 341 | UIO_FASTIOV, iovstack_r, |
ac34ebb3 | 342 | &iov_r); |
fcf63409 CY |
343 | if (rc <= 0) |
344 | goto free_iovecs; | |
345 | ||
9f78bdfa | 346 | rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); |
fcf63409 CY |
347 | |
348 | free_iovecs: | |
349 | if (iov_r != iovstack_r) | |
350 | kfree(iov_r); | |
17d17e72 | 351 | kfree(iov_l); |
fcf63409 CY |
352 | return rc; |
353 | } | |
354 | ||
2f2728f6 HC |
355 | COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid, |
356 | const struct compat_iovec __user *, lvec, | |
357 | compat_ulong_t, liovcnt, | |
358 | const struct compat_iovec __user *, rvec, | |
359 | compat_ulong_t, riovcnt, | |
360 | compat_ulong_t, flags) | |
fcf63409 CY |
361 | { |
362 | return compat_process_vm_rw(pid, lvec, liovcnt, rvec, | |
363 | riovcnt, flags, 0); | |
364 | } | |
365 | ||
2f2728f6 HC |
366 | COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid, |
367 | const struct compat_iovec __user *, lvec, | |
368 | compat_ulong_t, liovcnt, | |
369 | const struct compat_iovec __user *, rvec, | |
370 | compat_ulong_t, riovcnt, | |
371 | compat_ulong_t, flags) | |
fcf63409 CY |
372 | { |
373 | return compat_process_vm_rw(pid, lvec, liovcnt, rvec, | |
374 | riovcnt, flags, 1); | |
375 | } | |
376 | ||
377 | #endif |