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