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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * linux/mm/process_vm_access.c
4 *
5 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
6 */
7
8#include <linux/mm.h>
9#include <linux/uio.h>
10#include <linux/sched.h>
11#include <linux/sched/mm.h>
12#include <linux/highmem.h>
13#include <linux/ptrace.h>
14#include <linux/slab.h>
15#include <linux/syscalls.h>
16
17#ifdef CONFIG_COMPAT
18#include <linux/compat.h>
19#endif
20
21/**
22 * process_vm_rw_pages - read/write pages from task specified
23 * @pages: array of pointers to pages we want to copy
24 * @offset: offset in page to start copying from/to
25 * @len: number of bytes to copy
26 * @iter: where to copy to/from locally
27 * @vm_write: 0 means copy from, 1 means copy to
28 * Returns 0 on success, error code otherwise
29 */
30static int process_vm_rw_pages(struct page **pages,
31 unsigned offset,
32 size_t len,
33 struct iov_iter *iter,
34 int vm_write)
35{
36 /* Do the copy for each page */
37 while (len && iov_iter_count(iter)) {
38 struct page *page = *pages++;
39 size_t copy = PAGE_SIZE - offset;
40 size_t copied;
41
42 if (copy > len)
43 copy = len;
44
45 if (vm_write) {
46 copied = copy_page_from_iter(page, offset, copy, iter);
47 set_page_dirty_lock(page);
48 } else {
49 copied = copy_page_to_iter(page, offset, copy, iter);
50 }
51 len -= copied;
52 if (copied < copy && iov_iter_count(iter))
53 return -EFAULT;
54 offset = 0;
55 }
56 return 0;
57}
58
59/* Maximum number of pages kmalloc'd to hold struct page's during copy */
60#define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
61
62/**
63 * process_vm_rw_single_vec - read/write pages from task specified
64 * @addr: start memory address of target process
65 * @len: size of area to copy to/from
66 * @iter: where to copy to/from locally
67 * @process_pages: struct pages area that can store at least
68 * nr_pages_to_copy struct page pointers
69 * @mm: mm for task
70 * @task: task to read/write from
71 * @vm_write: 0 means copy from, 1 means copy to
72 * Returns 0 on success or on failure error code
73 */
74static int process_vm_rw_single_vec(unsigned long addr,
75 unsigned long len,
76 struct iov_iter *iter,
77 struct page **process_pages,
78 struct mm_struct *mm,
79 struct task_struct *task,
80 int vm_write)
81{
82 unsigned long pa = addr & PAGE_MASK;
83 unsigned long start_offset = addr - pa;
84 unsigned long nr_pages;
85 ssize_t rc = 0;
86 unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
87 / sizeof(struct pages *);
88 unsigned int flags = 0;
89
90 /* Work out address and page range required */
91 if (len == 0)
92 return 0;
93 nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
94
95 if (vm_write)
96 flags |= FOLL_WRITE;
97
98 while (!rc && nr_pages && iov_iter_count(iter)) {
99 int pages = min(nr_pages, max_pages_per_loop);
100 int locked = 1;
101 size_t bytes;
102
103 /*
104 * Get the pages we're interested in. We must
105 * access remotely because task/mm might not
106 * current/current->mm
107 */
108 down_read(&mm->mmap_sem);
109 pages = get_user_pages_remote(task, mm, pa, pages, flags,
110 process_pages, NULL, &locked);
111 if (locked)
112 up_read(&mm->mmap_sem);
113 if (pages <= 0)
114 return -EFAULT;
115
116 bytes = pages * PAGE_SIZE - start_offset;
117 if (bytes > len)
118 bytes = len;
119
120 rc = process_vm_rw_pages(process_pages,
121 start_offset, bytes, iter,
122 vm_write);
123 len -= bytes;
124 start_offset = 0;
125 nr_pages -= pages;
126 pa += pages * PAGE_SIZE;
127 while (pages)
128 put_page(process_pages[--pages]);
129 }
130
131 return rc;
132}
133
134/* Maximum number of entries for process pages array
135 which lives on stack */
136#define PVM_MAX_PP_ARRAY_COUNT 16
137
138/**
139 * process_vm_rw_core - core of reading/writing pages from task specified
140 * @pid: PID of process to read/write from/to
141 * @iter: where to copy to/from locally
142 * @rvec: iovec array specifying where to copy to/from in the other process
143 * @riovcnt: size of rvec array
144 * @flags: currently unused
145 * @vm_write: 0 if reading from other process, 1 if writing to other process
146 *
147 * Returns the number of bytes read/written or error code. May
148 * return less bytes than expected if an error occurs during the copying
149 * process.
150 */
151static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter,
152 const struct iovec *rvec,
153 unsigned long riovcnt,
154 unsigned long flags, int vm_write)
155{
156 struct task_struct *task;
157 struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT];
158 struct page **process_pages = pp_stack;
159 struct mm_struct *mm;
160 unsigned long i;
161 ssize_t rc = 0;
162 unsigned long nr_pages = 0;
163 unsigned long nr_pages_iov;
164 ssize_t iov_len;
165 size_t total_len = iov_iter_count(iter);
166
167 /*
168 * Work out how many pages of struct pages we're going to need
169 * when eventually calling get_user_pages
170 */
171 for (i = 0; i < riovcnt; i++) {
172 iov_len = rvec[i].iov_len;
173 if (iov_len > 0) {
174 nr_pages_iov = ((unsigned long)rvec[i].iov_base
175 + iov_len)
176 / PAGE_SIZE - (unsigned long)rvec[i].iov_base
177 / PAGE_SIZE + 1;
178 nr_pages = max(nr_pages, nr_pages_iov);
179 }
180 }
181
182 if (nr_pages == 0)
183 return 0;
184
185 if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) {
186 /* For reliability don't try to kmalloc more than
187 2 pages worth */
188 process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES,
189 sizeof(struct pages *)*nr_pages),
190 GFP_KERNEL);
191
192 if (!process_pages)
193 return -ENOMEM;
194 }
195
196 /* Get process information */
197 task = find_get_task_by_vpid(pid);
198 if (!task) {
199 rc = -ESRCH;
200 goto free_proc_pages;
201 }
202
203 mm = mm_access(task, PTRACE_MODE_ATTACH_REALCREDS);
204 if (!mm || IS_ERR(mm)) {
205 rc = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
206 /*
207 * Explicitly map EACCES to EPERM as EPERM is a more a
208 * appropriate error code for process_vw_readv/writev
209 */
210 if (rc == -EACCES)
211 rc = -EPERM;
212 goto put_task_struct;
213 }
214
215 for (i = 0; i < riovcnt && iov_iter_count(iter) && !rc; i++)
216 rc = process_vm_rw_single_vec(
217 (unsigned long)rvec[i].iov_base, rvec[i].iov_len,
218 iter, process_pages, mm, task, vm_write);
219
220 /* copied = space before - space after */
221 total_len -= iov_iter_count(iter);
222
223 /* If we have managed to copy any data at all then
224 we return the number of bytes copied. Otherwise
225 we return the error code */
226 if (total_len)
227 rc = total_len;
228
229 mmput(mm);
230
231put_task_struct:
232 put_task_struct(task);
233
234free_proc_pages:
235 if (process_pages != pp_stack)
236 kfree(process_pages);
237 return rc;
238}
239
240/**
241 * process_vm_rw - check iovecs before calling core routine
242 * @pid: PID of process to read/write from/to
243 * @lvec: iovec array specifying where to copy to/from locally
244 * @liovcnt: size of lvec array
245 * @rvec: iovec array specifying where to copy to/from in the other process
246 * @riovcnt: size of rvec array
247 * @flags: currently unused
248 * @vm_write: 0 if reading from other process, 1 if writing to other process
249 *
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;
265 struct iov_iter iter;
266 ssize_t rc;
267 int dir = vm_write ? WRITE : READ;
268
269 if (flags != 0)
270 return -EINVAL;
271
272 /* Check iovecs */
273 rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
274 if (rc < 0)
275 return rc;
276 if (!iov_iter_count(&iter))
277 goto free_iovecs;
278
279 rc = rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV,
280 iovstack_r, &iov_r);
281 if (rc <= 0)
282 goto free_iovecs;
283
284 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
285
286free_iovecs:
287 if (iov_r != iovstack_r)
288 kfree(iov_r);
289 kfree(iov_l);
290
291 return rc;
292}
293
294SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec,
295 unsigned long, liovcnt, const struct iovec __user *, rvec,
296 unsigned long, riovcnt, unsigned long, flags)
297{
298 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 0);
299}
300
301SYSCALL_DEFINE6(process_vm_writev, pid_t, pid,
302 const struct iovec __user *, lvec,
303 unsigned long, liovcnt, const struct iovec __user *, rvec,
304 unsigned long, riovcnt, unsigned long, flags)
305{
306 return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, 1);
307}
308
309#ifdef CONFIG_COMPAT
310
311static ssize_t
312compat_process_vm_rw(compat_pid_t pid,
313 const struct compat_iovec __user *lvec,
314 unsigned long liovcnt,
315 const struct compat_iovec __user *rvec,
316 unsigned long riovcnt,
317 unsigned long flags, int vm_write)
318{
319 struct iovec iovstack_l[UIO_FASTIOV];
320 struct iovec iovstack_r[UIO_FASTIOV];
321 struct iovec *iov_l = iovstack_l;
322 struct iovec *iov_r = iovstack_r;
323 struct iov_iter iter;
324 ssize_t rc = -EFAULT;
325 int dir = vm_write ? WRITE : READ;
326
327 if (flags != 0)
328 return -EINVAL;
329
330 rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
331 if (rc < 0)
332 return rc;
333 if (!iov_iter_count(&iter))
334 goto free_iovecs;
335 rc = compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY, rvec, riovcnt,
336 UIO_FASTIOV, iovstack_r,
337 &iov_r);
338 if (rc <= 0)
339 goto free_iovecs;
340
341 rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
342
343free_iovecs:
344 if (iov_r != iovstack_r)
345 kfree(iov_r);
346 kfree(iov_l);
347 return rc;
348}
349
350COMPAT_SYSCALL_DEFINE6(process_vm_readv, compat_pid_t, pid,
351 const struct compat_iovec __user *, lvec,
352 compat_ulong_t, liovcnt,
353 const struct compat_iovec __user *, rvec,
354 compat_ulong_t, riovcnt,
355 compat_ulong_t, flags)
356{
357 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
358 riovcnt, flags, 0);
359}
360
361COMPAT_SYSCALL_DEFINE6(process_vm_writev, 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)
367{
368 return compat_process_vm_rw(pid, lvec, liovcnt, rvec,
369 riovcnt, flags, 1);
370}
371
372#endif