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/compat.h> |
9 | #include <linux/mm.h> |
10 | #include <linux/uio.h> |
11 | #include <linux/sched.h> |
12 | #include <linux/sched/mm.h> |
13 | #include <linux/highmem.h> |
14 | #include <linux/ptrace.h> |
15 | #include <linux/slab.h> |
16 | #include <linux/syscalls.h> |
17 | |
18 | /** |
19 | * process_vm_rw_pages - read/write pages from task specified |
20 | * @pages: array of pointers to pages we want to copy |
21 | * @offset: offset in page to start copying from/to |
22 | * @len: number of bytes to copy |
23 | * @iter: where to copy to/from locally |
24 | * @vm_write: 0 means copy from, 1 means copy to |
25 | * Returns 0 on success, error code otherwise |
26 | */ |
27 | static int process_vm_rw_pages(struct page **pages, |
28 | unsigned offset, |
29 | size_t len, |
30 | struct iov_iter *iter, |
31 | int vm_write) |
32 | { |
33 | /* Do the copy for each page */ |
34 | while (len && iov_iter_count(i: iter)) { |
35 | struct page *page = *pages++; |
36 | size_t copy = PAGE_SIZE - offset; |
37 | size_t copied; |
38 | |
39 | if (copy > len) |
40 | copy = len; |
41 | |
42 | if (vm_write) |
43 | copied = copy_page_from_iter(page, offset, bytes: copy, i: iter); |
44 | else |
45 | copied = copy_page_to_iter(page, offset, bytes: copy, i: iter); |
46 | |
47 | len -= copied; |
48 | if (copied < copy && iov_iter_count(i: iter)) |
49 | return -EFAULT; |
50 | offset = 0; |
51 | } |
52 | return 0; |
53 | } |
54 | |
55 | /* Maximum number of pages kmalloc'd to hold struct page's during copy */ |
56 | #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2) |
57 | |
58 | /** |
59 | * process_vm_rw_single_vec - read/write pages from task specified |
60 | * @addr: start memory address of target process |
61 | * @len: size of area to copy to/from |
62 | * @iter: where to copy to/from locally |
63 | * @process_pages: struct pages area that can store at least |
64 | * nr_pages_to_copy struct page pointers |
65 | * @mm: mm for task |
66 | * @task: task to read/write from |
67 | * @vm_write: 0 means copy from, 1 means copy to |
68 | * Returns 0 on success or on failure error code |
69 | */ |
70 | static int process_vm_rw_single_vec(unsigned long addr, |
71 | unsigned long len, |
72 | struct iov_iter *iter, |
73 | struct page **process_pages, |
74 | struct mm_struct *mm, |
75 | struct task_struct *task, |
76 | int vm_write) |
77 | { |
78 | unsigned long pa = addr & PAGE_MASK; |
79 | unsigned long start_offset = addr - pa; |
80 | unsigned long nr_pages; |
81 | ssize_t rc = 0; |
82 | unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES |
83 | / sizeof(struct pages *); |
84 | unsigned int flags = 0; |
85 | |
86 | /* Work out address and page range required */ |
87 | if (len == 0) |
88 | return 0; |
89 | nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; |
90 | |
91 | if (vm_write) |
92 | flags |= FOLL_WRITE; |
93 | |
94 | while (!rc && nr_pages && iov_iter_count(i: iter)) { |
95 | int pinned_pages = min(nr_pages, max_pages_per_loop); |
96 | int locked = 1; |
97 | size_t bytes; |
98 | |
99 | /* |
100 | * Get the pages we're interested in. We must |
101 | * access remotely because task/mm might not |
102 | * current/current->mm |
103 | */ |
104 | mmap_read_lock(mm); |
105 | pinned_pages = pin_user_pages_remote(mm, start: pa, nr_pages: pinned_pages, |
106 | gup_flags: flags, pages: process_pages, |
107 | locked: &locked); |
108 | if (locked) |
109 | mmap_read_unlock(mm); |
110 | if (pinned_pages <= 0) |
111 | return -EFAULT; |
112 | |
113 | bytes = pinned_pages * PAGE_SIZE - start_offset; |
114 | if (bytes > len) |
115 | bytes = len; |
116 | |
117 | rc = process_vm_rw_pages(pages: process_pages, |
118 | offset: start_offset, len: bytes, iter, |
119 | vm_write); |
120 | len -= bytes; |
121 | start_offset = 0; |
122 | nr_pages -= pinned_pages; |
123 | pa += pinned_pages * PAGE_SIZE; |
124 | |
125 | /* If vm_write is set, the pages need to be made dirty: */ |
126 | unpin_user_pages_dirty_lock(pages: process_pages, npages: pinned_pages, |
127 | make_dirty: vm_write); |
128 | } |
129 | |
130 | return rc; |
131 | } |
132 | |
133 | /* Maximum number of entries for process pages array |
134 | which lives on stack */ |
135 | #define PVM_MAX_PP_ARRAY_COUNT 16 |
136 | |
137 | /** |
138 | * process_vm_rw_core - core of reading/writing pages from task specified |
139 | * @pid: PID of process to read/write from/to |
140 | * @iter: where to copy to/from locally |
141 | * @rvec: iovec array specifying where to copy to/from in the other process |
142 | * @riovcnt: size of rvec array |
143 | * @flags: currently unused |
144 | * @vm_write: 0 if reading from other process, 1 if writing to other process |
145 | * |
146 | * Returns the number of bytes read/written or error code. May |
147 | * return less bytes than expected if an error occurs during the copying |
148 | * process. |
149 | */ |
150 | static ssize_t process_vm_rw_core(pid_t pid, struct iov_iter *iter, |
151 | const struct iovec *rvec, |
152 | unsigned long riovcnt, |
153 | unsigned long flags, int vm_write) |
154 | { |
155 | struct task_struct *task; |
156 | struct page *pp_stack[PVM_MAX_PP_ARRAY_COUNT]; |
157 | struct page **process_pages = pp_stack; |
158 | struct mm_struct *mm; |
159 | unsigned long i; |
160 | ssize_t rc = 0; |
161 | unsigned long nr_pages = 0; |
162 | unsigned long nr_pages_iov; |
163 | ssize_t iov_len; |
164 | size_t total_len = iov_iter_count(i: iter); |
165 | |
166 | /* |
167 | * Work out how many pages of struct pages we're going to need |
168 | * when eventually calling get_user_pages |
169 | */ |
170 | for (i = 0; i < riovcnt; i++) { |
171 | iov_len = rvec[i].iov_len; |
172 | if (iov_len > 0) { |
173 | nr_pages_iov = ((unsigned long)rvec[i].iov_base |
174 | + iov_len) |
175 | / PAGE_SIZE - (unsigned long)rvec[i].iov_base |
176 | / PAGE_SIZE + 1; |
177 | nr_pages = max(nr_pages, nr_pages_iov); |
178 | } |
179 | } |
180 | |
181 | if (nr_pages == 0) |
182 | return 0; |
183 | |
184 | if (nr_pages > PVM_MAX_PP_ARRAY_COUNT) { |
185 | /* For reliability don't try to kmalloc more than |
186 | 2 pages worth */ |
187 | process_pages = kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES, |
188 | sizeof(struct pages *)*nr_pages), |
189 | GFP_KERNEL); |
190 | |
191 | if (!process_pages) |
192 | return -ENOMEM; |
193 | } |
194 | |
195 | /* Get process information */ |
196 | task = find_get_task_by_vpid(nr: pid); |
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(ptr: mm)) { |
204 | rc = IS_ERR(ptr: mm) ? PTR_ERR(ptr: mm) : -ESRCH; |
205 | /* |
206 | * Explicitly map EACCES to EPERM as EPERM is a more |
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(i: iter) && !rc; i++) |
215 | rc = process_vm_rw_single_vec( |
216 | addr: (unsigned long)rvec[i].iov_base, len: 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(i: 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(t: task); |
232 | |
233 | free_proc_pages: |
234 | if (process_pages != pp_stack) |
235 | kfree(objp: 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 | * |
249 | * Returns the number of bytes read/written or error code. May |
250 | * return less bytes than expected if an error occurs during the copying |
251 | * process. |
252 | */ |
253 | static ssize_t process_vm_rw(pid_t pid, |
254 | const struct iovec __user *lvec, |
255 | unsigned long liovcnt, |
256 | const struct iovec __user *rvec, |
257 | unsigned long riovcnt, |
258 | unsigned long flags, int vm_write) |
259 | { |
260 | struct iovec iovstack_l[UIO_FASTIOV]; |
261 | struct iovec iovstack_r[UIO_FASTIOV]; |
262 | struct iovec *iov_l = iovstack_l; |
263 | struct iovec *iov_r; |
264 | struct iov_iter iter; |
265 | ssize_t rc; |
266 | int dir = vm_write ? ITER_SOURCE : ITER_DEST; |
267 | |
268 | if (flags != 0) |
269 | return -EINVAL; |
270 | |
271 | /* Check iovecs */ |
272 | rc = import_iovec(type: dir, uvec: lvec, nr_segs: liovcnt, UIO_FASTIOV, iovp: &iov_l, i: &iter); |
273 | if (rc < 0) |
274 | return rc; |
275 | if (!iov_iter_count(i: &iter)) |
276 | goto free_iov_l; |
277 | iov_r = iovec_from_user(uvector: rvec, nr_segs: riovcnt, UIO_FASTIOV, fast_iov: iovstack_r, |
278 | in_compat_syscall()); |
279 | if (IS_ERR(ptr: iov_r)) { |
280 | rc = PTR_ERR(ptr: iov_r); |
281 | goto free_iov_l; |
282 | } |
283 | rc = process_vm_rw_core(pid, iter: &iter, rvec: iov_r, riovcnt, flags, vm_write); |
284 | if (iov_r != iovstack_r) |
285 | kfree(objp: iov_r); |
286 | free_iov_l: |
287 | kfree(objp: iov_l); |
288 | return rc; |
289 | } |
290 | |
291 | SYSCALL_DEFINE6(process_vm_readv, pid_t, pid, const struct iovec __user *, lvec, |
292 | unsigned long, liovcnt, const struct iovec __user *, rvec, |
293 | unsigned long, riovcnt, unsigned long, flags) |
294 | { |
295 | return process_vm_rw(pid, lvec, liovcnt, rvec, riovcnt, flags, vm_write: 0); |
296 | } |
297 | |
298 | SYSCALL_DEFINE6(process_vm_writev, pid_t, pid, |
299 | 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, vm_write: 1); |
304 | } |
305 | |