2 * linux/mm/process_vm_access.c
4 * Copyright (C) 2010-2011 Christopher Yeoh <cyeoh@au1.ibm.com>, IBM Corp.
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.
13 #include <linux/uio.h>
14 #include <linux/sched.h>
15 #include <linux/sched/mm.h>
16 #include <linux/highmem.h>
17 #include <linux/ptrace.h>
18 #include <linux/slab.h>
19 #include <linux/syscalls.h>
22 #include <linux/compat.h>
26 * process_vm_rw_pages - read/write pages from task specified
27 * @pages: array of pointers to pages we want to copy
28 * @start_offset: offset in page to start copying from/to
29 * @len: number of bytes to copy
30 * @iter: where to copy to/from locally
31 * @vm_write: 0 means copy from, 1 means copy to
32 * Returns 0 on success, error code otherwise
34 static int process_vm_rw_pages(struct page
**pages
,
37 struct iov_iter
*iter
,
40 /* Do the copy for each page */
41 while (len
&& iov_iter_count(iter
)) {
42 struct page
*page
= *pages
++;
43 size_t copy
= PAGE_SIZE
- offset
;
50 copied
= copy_page_from_iter(page
, offset
, copy
, iter
);
51 set_page_dirty_lock(page
);
53 copied
= copy_page_to_iter(page
, offset
, copy
, iter
);
56 if (copied
< copy
&& iov_iter_count(iter
))
63 /* Maximum number of pages kmalloc'd to hold struct page's during copy */
64 #define PVM_MAX_KMALLOC_PAGES (PAGE_SIZE * 2)
67 * process_vm_rw_single_vec - read/write pages from task specified
68 * @addr: start memory address of target process
69 * @len: size of area to copy to/from
70 * @iter: where to copy to/from locally
71 * @process_pages: struct pages area that can store at least
72 * nr_pages_to_copy struct page pointers
74 * @task: task to read/write from
75 * @vm_write: 0 means copy from, 1 means copy to
76 * Returns 0 on success or on failure error code
78 static int process_vm_rw_single_vec(unsigned long addr
,
80 struct iov_iter
*iter
,
81 struct page
**process_pages
,
83 struct task_struct
*task
,
86 unsigned long pa
= addr
& PAGE_MASK
;
87 unsigned long start_offset
= addr
- pa
;
88 unsigned long nr_pages
;
90 unsigned long max_pages_per_loop
= PVM_MAX_KMALLOC_PAGES
91 / sizeof(struct pages
*);
92 unsigned int flags
= 0;
94 /* Work out address and page range required */
97 nr_pages
= (addr
+ len
- 1) / PAGE_SIZE
- addr
/ PAGE_SIZE
+ 1;
102 while (!rc
&& nr_pages
&& iov_iter_count(iter
)) {
103 int pages
= min(nr_pages
, max_pages_per_loop
);
108 * Get the pages we're interested in. We must
109 * access remotely because task/mm might not
110 * current/current->mm
112 down_read(&mm
->mmap_sem
);
113 pages
= get_user_pages_remote(task
, mm
, pa
, pages
, flags
,
114 process_pages
, NULL
, &locked
);
116 up_read(&mm
->mmap_sem
);
120 bytes
= pages
* PAGE_SIZE
- start_offset
;
124 rc
= process_vm_rw_pages(process_pages
,
125 start_offset
, bytes
, iter
,
130 pa
+= pages
* PAGE_SIZE
;
132 put_page(process_pages
[--pages
]);
138 /* Maximum number of entries for process pages array
139 which lives on stack */
140 #define PVM_MAX_PP_ARRAY_COUNT 16
143 * process_vm_rw_core - core of reading/writing pages from task specified
144 * @pid: PID of process to read/write from/to
145 * @iter: where to copy to/from locally
146 * @rvec: iovec array specifying where to copy to/from in the other process
147 * @riovcnt: size of rvec array
148 * @flags: currently unused
149 * @vm_write: 0 if reading from other process, 1 if writing to other process
150 * Returns the number of bytes read/written or error code. May
151 * return less bytes than expected if an error occurs during the copying
154 static ssize_t
process_vm_rw_core(pid_t pid
, struct iov_iter
*iter
,
155 const struct iovec
*rvec
,
156 unsigned long riovcnt
,
157 unsigned long flags
, int vm_write
)
159 struct task_struct
*task
;
160 struct page
*pp_stack
[PVM_MAX_PP_ARRAY_COUNT
];
161 struct page
**process_pages
= pp_stack
;
162 struct mm_struct
*mm
;
165 unsigned long nr_pages
= 0;
166 unsigned long nr_pages_iov
;
168 size_t total_len
= iov_iter_count(iter
);
171 * Work out how many pages of struct pages we're going to need
172 * when eventually calling get_user_pages
174 for (i
= 0; i
< riovcnt
; i
++) {
175 iov_len
= rvec
[i
].iov_len
;
177 nr_pages_iov
= ((unsigned long)rvec
[i
].iov_base
179 / PAGE_SIZE
- (unsigned long)rvec
[i
].iov_base
181 nr_pages
= max(nr_pages
, nr_pages_iov
);
188 if (nr_pages
> PVM_MAX_PP_ARRAY_COUNT
) {
189 /* For reliability don't try to kmalloc more than
191 process_pages
= kmalloc(min_t(size_t, PVM_MAX_KMALLOC_PAGES
,
192 sizeof(struct pages
*)*nr_pages
),
199 /* Get process information */
201 task
= find_task_by_vpid(pid
);
203 get_task_struct(task
);
207 goto free_proc_pages
;
210 mm
= mm_access(task
, PTRACE_MODE_ATTACH_REALCREDS
);
211 if (!mm
|| IS_ERR(mm
)) {
212 rc
= IS_ERR(mm
) ? PTR_ERR(mm
) : -ESRCH
;
214 * Explicitly map EACCES to EPERM as EPERM is a more a
215 * appropriate error code for process_vw_readv/writev
219 goto put_task_struct
;
222 for (i
= 0; i
< riovcnt
&& iov_iter_count(iter
) && !rc
; i
++)
223 rc
= process_vm_rw_single_vec(
224 (unsigned long)rvec
[i
].iov_base
, rvec
[i
].iov_len
,
225 iter
, process_pages
, mm
, task
, vm_write
);
227 /* copied = space before - space after */
228 total_len
-= iov_iter_count(iter
);
230 /* If we have managed to copy any data at all then
231 we return the number of bytes copied. Otherwise
232 we return the error code */
239 put_task_struct(task
);
242 if (process_pages
!= pp_stack
)
243 kfree(process_pages
);
248 * process_vm_rw - check iovecs before calling core routine
249 * @pid: PID of process to read/write from/to
250 * @lvec: iovec array specifying where to copy to/from locally
251 * @liovcnt: size of lvec array
252 * @rvec: iovec array specifying where to copy to/from in the other process
253 * @riovcnt: size of rvec array
254 * @flags: currently unused
255 * @vm_write: 0 if reading from other process, 1 if writing to other process
256 * Returns the number of bytes read/written or error code. May
257 * return less bytes than expected if an error occurs during the copying
260 static ssize_t
process_vm_rw(pid_t pid
,
261 const struct iovec __user
*lvec
,
262 unsigned long liovcnt
,
263 const struct iovec __user
*rvec
,
264 unsigned long riovcnt
,
265 unsigned long flags
, int vm_write
)
267 struct iovec iovstack_l
[UIO_FASTIOV
];
268 struct iovec iovstack_r
[UIO_FASTIOV
];
269 struct iovec
*iov_l
= iovstack_l
;
270 struct iovec
*iov_r
= iovstack_r
;
271 struct iov_iter iter
;
273 int dir
= vm_write
? WRITE
: READ
;
279 rc
= import_iovec(dir
, lvec
, liovcnt
, UIO_FASTIOV
, &iov_l
, &iter
);
282 if (!iov_iter_count(&iter
))
285 rc
= rw_copy_check_uvector(CHECK_IOVEC_ONLY
, rvec
, riovcnt
, UIO_FASTIOV
,
290 rc
= process_vm_rw_core(pid
, &iter
, iov_r
, riovcnt
, flags
, vm_write
);
293 if (iov_r
!= iovstack_r
)
300 SYSCALL_DEFINE6(process_vm_readv
, pid_t
, pid
, const struct iovec __user
*, lvec
,
301 unsigned long, liovcnt
, const struct iovec __user
*, rvec
,
302 unsigned long, riovcnt
, unsigned long, flags
)
304 return process_vm_rw(pid
, lvec
, liovcnt
, rvec
, riovcnt
, flags
, 0);
307 SYSCALL_DEFINE6(process_vm_writev
, pid_t
, pid
,
308 const struct iovec __user
*, lvec
,
309 unsigned long, liovcnt
, const struct iovec __user
*, rvec
,
310 unsigned long, riovcnt
, unsigned long, flags
)
312 return process_vm_rw(pid
, lvec
, liovcnt
, rvec
, riovcnt
, flags
, 1);
318 compat_process_vm_rw(compat_pid_t pid
,
319 const struct compat_iovec __user
*lvec
,
320 unsigned long liovcnt
,
321 const struct compat_iovec __user
*rvec
,
322 unsigned long riovcnt
,
323 unsigned long flags
, int vm_write
)
325 struct iovec iovstack_l
[UIO_FASTIOV
];
326 struct iovec iovstack_r
[UIO_FASTIOV
];
327 struct iovec
*iov_l
= iovstack_l
;
328 struct iovec
*iov_r
= iovstack_r
;
329 struct iov_iter iter
;
330 ssize_t rc
= -EFAULT
;
331 int dir
= vm_write
? WRITE
: READ
;
336 rc
= compat_import_iovec(dir
, lvec
, liovcnt
, UIO_FASTIOV
, &iov_l
, &iter
);
339 if (!iov_iter_count(&iter
))
341 rc
= compat_rw_copy_check_uvector(CHECK_IOVEC_ONLY
, rvec
, riovcnt
,
342 UIO_FASTIOV
, iovstack_r
,
347 rc
= process_vm_rw_core(pid
, &iter
, iov_r
, riovcnt
, flags
, vm_write
);
350 if (iov_r
!= iovstack_r
)
356 COMPAT_SYSCALL_DEFINE6(process_vm_readv
, compat_pid_t
, pid
,
357 const struct compat_iovec __user
*, lvec
,
358 compat_ulong_t
, liovcnt
,
359 const struct compat_iovec __user
*, rvec
,
360 compat_ulong_t
, riovcnt
,
361 compat_ulong_t
, flags
)
363 return compat_process_vm_rw(pid
, lvec
, liovcnt
, rvec
,
367 COMPAT_SYSCALL_DEFINE6(process_vm_writev
, compat_pid_t
, pid
,
368 const struct compat_iovec __user
*, lvec
,
369 compat_ulong_t
, liovcnt
,
370 const struct compat_iovec __user
*, rvec
,
371 compat_ulong_t
, riovcnt
,
372 compat_ulong_t
, flags
)
374 return compat_process_vm_rw(pid
, lvec
, liovcnt
, rvec
,