Merge tag 'sound-5.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai...
[platform/kernel/linux-rpi.git] / mm / process_vm_access.c
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(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, copy, iter);
44                 else
45                         copied = copy_page_to_iter(page, offset, copy, iter);
46
47                 len -= copied;
48                 if (copied < copy && iov_iter_count(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(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, pa, pinned_pages,
106                                                      flags, process_pages,
107                                                      NULL, &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(process_pages,
118                                          start_offset, 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(process_pages, pinned_pages,
127                                             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(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(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(mm)) {
204                 rc = IS_ERR(mm) ? PTR_ERR(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(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  *
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 ? WRITE : READ;
267
268         if (flags != 0)
269                 return -EINVAL;
270
271         /* Check iovecs */
272         rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter);
273         if (rc < 0)
274                 return rc;
275         if (!iov_iter_count(&iter))
276                 goto free_iov_l;
277         iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r,
278                                 in_compat_syscall());
279         if (IS_ERR(iov_r)) {
280                 rc = PTR_ERR(iov_r);
281                 goto free_iov_l;
282         }
283         rc = process_vm_rw_core(pid, &iter, iov_r, riovcnt, flags, vm_write);
284         if (iov_r != iovstack_r)
285                 kfree(iov_r);
286 free_iov_l:
287         kfree(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, 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, 1);
304 }