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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 | |
26 | * @pages: array of pointers to pages we want to copy | |
27 | * @start_offset: offset in page to start copying from/to | |
28 | * @len: number of bytes to copy | |
29 | * @iter: where to copy to/from locally | |
30 | * @vm_write: 0 means copy from, 1 means copy to | |
31 | * Returns 0 on success, error code otherwise | |
32 | */ | |
33 | static int process_vm_rw_pages(struct page **pages, | |
34 | unsigned offset, | |
35 | size_t len, | |
36 | struct iov_iter *iter, | |
37 | int vm_write) | |
38 | { | |
39 | /* Do the copy for each page */ | |
40 | while (len && iov_iter_count(iter)) { | |
41 | struct page *page = *pages++; | |
42 | size_t copy = PAGE_SIZE - offset; | |
43 | size_t copied; | |
44 | ||
45 | if (copy > len) | |
46 | copy = len; | |
47 | ||
48 | if (vm_write) { | |
49 | copied = copy_page_from_iter(page, offset, copy, iter); | |
50 | set_page_dirty_lock(page); | |
51 | } else { | |
52 | copied = copy_page_to_iter(page, offset, copy, iter); | |
53 | } | |
54 | len -= copied; | |
55 | if (copied < copy && iov_iter_count(iter)) | |
56 | return -EFAULT; | |
57 | offset = 0; | |
58 | } | |
59 | return 0; | |
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 | |
69 | * @iter: where to copy to/from locally | |
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 | |
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, | |
79 | struct iov_iter *iter, | |
80 | struct page **process_pages, | |
81 | struct mm_struct *mm, | |
82 | struct task_struct *task, | |
83 | int vm_write) | |
84 | { | |
85 | unsigned long pa = addr & PAGE_MASK; | |
86 | unsigned long start_offset = addr - pa; | |
87 | unsigned long nr_pages; | |
88 | ssize_t rc = 0; | |
89 | unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES | |
90 | / sizeof(struct pages *); | |
91 | ||
92 | /* Work out address and page range required */ | |
93 | if (len == 0) | |
94 | return 0; | |
95 | nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; | |
96 | ||
97 | while (!rc && nr_pages && iov_iter_count(iter)) { | |
98 | int pages = min(nr_pages, max_pages_per_loop); | |
99 | size_t bytes; | |
100 | ||
101 | /* | |
102 | * Get the pages we're interested in. We must | |
103 | * add FOLL_REMOTE because task/mm might not | |
104 | * current/current->mm | |
105 | */ | |
106 | pages = __get_user_pages_unlocked(task, mm, pa, pages, | |
107 | vm_write, 0, process_pages, | |
108 | FOLL_REMOTE); | |
109 | if (pages <= 0) | |
110 | return -EFAULT; | |
111 | ||
112 | bytes = pages * PAGE_SIZE - start_offset; | |
113 | if (bytes > len) | |
114 | bytes = len; | |
115 | ||
116 | rc = process_vm_rw_pages(process_pages, | |
117 | start_offset, bytes, iter, | |
118 | vm_write); | |
119 | len -= bytes; | |
120 | start_offset = 0; | |
121 | nr_pages -= pages; | |
122 | pa += pages * PAGE_SIZE; | |
123 | while (pages) | |
124 | put_page(process_pages[--pages]); | |
125 | } | |
126 | ||
127 | return rc; | |
128 | } | |
129 | ||
130 | /* Maximum number of entries for process pages array | |
131 | which lives on stack */ | |
132 | #define PVM_MAX_PP_ARRAY_COUNT 16 | |
133 | ||
134 | /** | |
135 | * process_vm_rw_core - core of reading/writing pages from task specified | |
136 | * @pid: PID of process to read/write from/to | |
137 | * @iter: where to copy to/from locally | |
138 | * @rvec: iovec array specifying where to copy to/from in the other process | |
139 | * @riovcnt: size of rvec array | |
140 | * @flags: currently unused | |
141 | * @vm_write: 0 if reading from other process, 1 if writing to other process | |
142 | * Returns the number of bytes read/written or error code. May | |
143 | * return less bytes than expected if an error occurs during the copying | |
144 | * process. | |
145 | */ | |
146 | static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, | |
147 | const struct iovec *rvec, | |
148 | unsigned long riovcnt, | |
149 | unsigned long flags, int vm_write) | |
150 | { | |
151 | struct task_struct *task; | |
152 | struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; | |
153 | struct page **process_pages = pp_stack; | |
154 | struct mm_struct *mm; | |
155 | unsigned long i; | |
156 | ssize_t rc = 0; | |
157 | unsigned long nr_pages = 0; | |
158 | unsigned long nr_pages_iov; | |
159 | ssize_t iov_len; | |
160 | size_t total_len = iov_iter_count(iter); | |
161 | ||
162 | /* | |
163 | * Work out how many pages of struct pages we're going to need | |
164 | * when eventually calling get_user_pages | |
165 | */ | |
166 | for (i = 0; i < riovcnt; i++) { | |
167 | iov_len = rvec[i].iov_len; | |
168 | if (iov_len > 0) { | |
169 | nr_pages_iov = ((unsigned long)rvec[i].iov_base | |
170 | + iov_len) | |
171 | / PAGE_SIZE - (unsigned long)rvec[i].iov_base | |
172 | / PAGE_SIZE + 1; | |
173 | nr_pages = max(nr_pages, nr_pages_iov); | |
174 | } | |
175 | } | |
176 | ||
177 | if (nr_pages == 0) | |
178 | return 0; | |
179 | ||
180 | if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { | |
181 | /* For reliability don't try to kmalloc more than | |
182 | 2 pages worth */ | |
183 | process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, | |
184 | sizeof(struct pages *)*nr_pages), | |
185 | GFP_KERNEL); | |
186 | ||
187 | if (!process_pages) | |
188 | return -ENOMEM; | |
189 | } | |
190 | ||
191 | /* Get process information */ | |
192 | rcu_read_lock(); | |
193 | task = find_task_by_vpid(pid); | |
194 | if (task) | |
195 | get_task_struct(task); | |
196 | rcu_read_unlock(); | |
197 | if (!task) { | |
198 | rc = -ESRCH; | |
199 | goto free_proc_pages; | |
200 | } | |
201 | ||
202 | mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS); | |
203 | if (!mm || IS_ERR(mm)) { | |
204 | rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH; | |
205 | /* | |
206 | * Explicitly map EACCES to EPERM as EPERM is a more a | |
207 | * appropriate error code for process_vw_readv/writev | |
208 | */ | |
209 | if (rc == -EACCES) | |
210 | rc = -EPERM; | |
211 | goto put_task_struct; | |
212 | } | |
213 | ||
214 | for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++) | |
215 | rc = process_vm_rw_single_vec( | |
216 | (unsigned long)rvec[i].iov_base, rvec[i].iov_len, | |
217 | iter, process_pages, mm, task, vm_write); | |
218 | ||
219 | /* copied = space before - space after */ | |
220 | total_len -= iov_iter_count(iter); | |
221 | ||
222 | /* If we have managed to copy any data at all then | |
223 | we return the number of bytes copied. Otherwise | |
224 | we return the error code */ | |
225 | if (total_len) | |
226 | rc = total_len; | |
227 | ||
228 | mmput(mm); | |
229 | ||
230 | put_task_struct: | |
231 | put_task_struct(task); | |
232 | ||
233 | free_proc_pages: | |
234 | if (process_pages != pp_stack) | |
235 | kfree(process_pages); | |
236 | return rc; | |
237 | } | |
238 | ||
239 | /** | |
240 | * process_vm_rw - check iovecs before calling core routine | |
241 | * @pid: PID of process to read/write from/to | |
242 | * @lvec: iovec array specifying where to copy to/from locally | |
243 | * @liovcnt: size of lvec array | |
244 | * @rvec: iovec array specifying where to copy to/from in the other process | |
245 | * @riovcnt: size of rvec array | |
246 | * @flags: currently unused | |
247 | * @vm_write: 0 if reading from other process, 1 if writing to other process | |
248 | * Returns the number of bytes read/written or error code. May | |
249 | * return less bytes than expected if an error occurs during the copying | |
250 | * process. | |
251 | */ | |
252 | static ssize_t process_vm_rw(pid_t pid, | |
253 | const struct iovec __user *lvec, | |
254 | unsigned long liovcnt, | |
255 | const struct iovec __user *rvec, | |
256 | unsigned long riovcnt, | |
257 | unsigned long flags, int vm_write) | |
258 | { | |
259 | struct iovec iovstack_l[UIO_FASTIOV]; | |
260 | struct iovec iovstack_r[UIO_FASTIOV]; | |
261 | struct iovec *iov_l = iovstack_l; | |
262 | struct iovec *iov_r = iovstack_r; | |
263 | struct iov_iter iter; | |
264 | ssize_t rc; | |
265 | int dir = vm_write ? WRITE : READ; | |
266 | ||
267 | if (flags != 0) | |
268 | return -EINVAL; | |
269 | ||
270 | /* Check iovecs */ | |
271 | rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); | |
272 | if (rc < 0) | |
273 | return rc; | |
274 | if (!iov_iter_count(&iter)) | |
275 | goto free_iovecs; | |
276 | ||
277 | rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV, | |
278 | iovstack_r, &iov_r); | |
279 | if (rc <= 0) | |
280 | goto free_iovecs; | |
281 | ||
282 | rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); | |
283 | ||
284 | free_iovecs: | |
285 | if (iov_r != iovstack_r) | |
286 | kfree(iov_r); | |
287 | kfree(iov_l); | |
288 | ||
289 | return rc; | |
290 | } | |
291 | ||
292 | SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, | |
293 | unsigned long, liovcnt, const struct iovec __user *, rvec, | |
294 | unsigned long, riovcnt, unsigned long, flags) | |
295 | { | |
296 | return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0); | |
297 | } | |
298 | ||
299 | SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, | |
300 | const struct iovec __user *, lvec, | |
301 | unsigned long, liovcnt, const struct iovec __user *, rvec, | |
302 | unsigned long, riovcnt, unsigned long, flags) | |
303 | { | |
304 | return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1); | |
305 | } | |
306 | ||
307 | #ifdef CONFIG_COMPAT | |
308 | ||
309 | static ssize_t | |
310 | compat_process_vm_rw(compat_pid_t pid, | |
311 | const struct compat_iovec __user *lvec, | |
312 | unsigned long liovcnt, | |
313 | const struct compat_iovec __user *rvec, | |
314 | unsigned long riovcnt, | |
315 | unsigned long flags, int vm_write) | |
316 | { | |
317 | struct iovec iovstack_l[UIO_FASTIOV]; | |
318 | struct iovec iovstack_r[UIO_FASTIOV]; | |
319 | struct iovec *iov_l = iovstack_l; | |
320 | struct iovec *iov_r = iovstack_r; | |
321 | struct iov_iter iter; | |
322 | ssize_t rc = -EFAULT; | |
323 | int dir = vm_write ? WRITE : READ; | |
324 | ||
325 | if (flags != 0) | |
326 | return -EINVAL; | |
327 | ||
328 | rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter); | |
329 | if (rc < 0) | |
330 | return rc; | |
331 | if (!iov_iter_count(&iter)) | |
332 | goto free_iovecs; | |
333 | rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, | |
334 | UIO_FASTIOV, iovstack_r, | |
335 | &iov_r); | |
336 | if (rc <= 0) | |
337 | goto free_iovecs; | |
338 | ||
339 | rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write); | |
340 | ||
341 | free_iovecs: | |
342 | if (iov_r != iovstack_r) | |
343 | kfree(iov_r); | |
344 | kfree(iov_l); | |
345 | return rc; | |
346 | } | |
347 | ||
348 | COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid, | |
349 | const struct compat_iovec __user *, lvec, | |
350 | compat_ulong_t, liovcnt, | |
351 | const struct compat_iovec __user *, rvec, | |
352 | compat_ulong_t, riovcnt, | |
353 | compat_ulong_t, flags) | |
354 | { | |
355 | return compat_process_vm_rw(pid, lvec, liovcnt, rvec, | |
356 | riovcnt, flags, 0); | |
357 | } | |
358 | ||
359 | COMPAT_SYSCALL_DEFINE6(process_vm_writev, compat_pid_t, pid, | |
360 | const struct compat_iovec __user *, lvec, | |
361 | compat_ulong_t, liovcnt, | |
362 | const struct compat_iovec __user *, rvec, | |
363 | compat_ulong_t, riovcnt, | |
364 | compat_ulong_t, flags) | |
365 | { | |
366 | return compat_process_vm_rw(pid, lvec, liovcnt, rvec, | |
367 | riovcnt, flags, 1); | |
368 | } | |
369 | ||
370 | #endif |