1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/fs/readdir.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 */
7
8 #include <linux/stddef.h>
9 #include <linux/kernel.h>
10 #include <linux/export.h>
11 #include <linux/time.h>
12 #include <linux/mm.h>
13 #include <linux/errno.h>
14 #include <linux/stat.h>
15 #include <linux/file.h>
16 #include <linux/fs.h>
17 #include <linux/fsnotify.h>
18 #include <linux/dirent.h>
19 #include <linux/security.h>
20 #include <linux/syscalls.h>
21 #include <linux/unistd.h>
22 #include <linux/compat.h>
23 #include <linux/uaccess.h>
24
25 #include <asm/unaligned.h>
26
27 /*
28 * Note the "unsafe_put_user() semantics: we goto a
29 * label for errors.
30 */
31 #define unsafe_copy_dirent_name(_dst, _src, _len, label) do { \
32 char __user *dst = (_dst); \
33 const char *src = (_src); \
34 size_t len = (_len); \
35 unsafe_put_user(0, dst+len, label); \
36 unsafe_copy_to_user(dst, src, len, label); \
37 } while (0)
38
39
iterate_dir(struct file * file,struct dir_context * ctx)40 int iterate_dir(struct file *file, struct dir_context *ctx)
41 {
42 struct inode *inode = file_inode(file);
43 bool shared = false;
44 int res = -ENOTDIR;
45 if (file->f_op->iterate_shared)
46 shared = true;
47 else if (!file->f_op->iterate)
48 goto out;
49
50 res = security_file_permission(file, MAY_READ);
51 if (res)
52 goto out;
53
54 if (shared)
55 res = down_read_killable(&inode->i_rwsem);
56 else
57 res = down_write_killable(&inode->i_rwsem);
58 if (res)
59 goto out;
60
61 res = -ENOENT;
62 if (!IS_DEADDIR(inode)) {
63 ctx->pos = file->f_pos;
64 if (shared)
65 res = file->f_op->iterate_shared(file, ctx);
66 else
67 res = file->f_op->iterate(file, ctx);
68 file->f_pos = ctx->pos;
69 fsnotify_access(file);
70 file_accessed(file);
71 }
72 if (shared)
73 inode_unlock_shared(inode);
74 else
75 inode_unlock(inode);
76 out:
77 return res;
78 }
79 EXPORT_SYMBOL(iterate_dir);
80
81 /*
82 * POSIX says that a dirent name cannot contain NULL or a '/'.
83 *
84 * It's not 100% clear what we should really do in this case.
85 * The filesystem is clearly corrupted, but returning a hard
86 * error means that you now don't see any of the other names
87 * either, so that isn't a perfect alternative.
88 *
89 * And if you return an error, what error do you use? Several
90 * filesystems seem to have decided on EUCLEAN being the error
91 * code for EFSCORRUPTED, and that may be the error to use. Or
92 * just EIO, which is perhaps more obvious to users.
93 *
94 * In order to see the other file names in the directory, the
95 * caller might want to make this a "soft" error: skip the
96 * entry, and return the error at the end instead.
97 *
98 * Note that this should likely do a "memchr(name, 0, len)"
99 * check too, since that would be filesystem corruption as
100 * well. However, that case can't actually confuse user space,
101 * which has to do a strlen() on the name anyway to find the
102 * filename length, and the above "soft error" worry means
103 * that it's probably better left alone until we have that
104 * issue clarified.
105 *
106 * Note the PATH_MAX check - it's arbitrary but the real
107 * kernel limit on a possible path component, not NAME_MAX,
108 * which is the technical standard limit.
109 */
verify_dirent_name(const char * name,int len)110 static int verify_dirent_name(const char *name, int len)
111 {
112 if (len <= 0 || len >= PATH_MAX)
113 return -EIO;
114 if (memchr(name, '/', len))
115 return -EIO;
116 return 0;
117 }
118
119 /*
120 * Traditional linux readdir() handling..
121 *
122 * "count=1" is a special case, meaning that the buffer is one
123 * dirent-structure in size and that the code can't handle more
124 * anyway. Thus the special "fillonedir()" function for that
125 * case (the low-level handlers don't need to care about this).
126 */
127
128 #ifdef __ARCH_WANT_OLD_READDIR
129
130 struct old_linux_dirent {
131 unsigned long d_ino;
132 unsigned long d_offset;
133 unsigned short d_namlen;
134 char d_name[1];
135 };
136
137 struct readdir_callback {
138 struct dir_context ctx;
139 struct old_linux_dirent __user * dirent;
140 int result;
141 };
142
fillonedir(struct dir_context * ctx,const char * name,int namlen,loff_t offset,u64 ino,unsigned int d_type)143 static int fillonedir(struct dir_context *ctx, const char *name, int namlen,
144 loff_t offset, u64 ino, unsigned int d_type)
145 {
146 struct readdir_callback *buf =
147 container_of(ctx, struct readdir_callback, ctx);
148 struct old_linux_dirent __user * dirent;
149 unsigned long d_ino;
150
151 if (buf->result)
152 return -EINVAL;
153 buf->result = verify_dirent_name(name, namlen);
154 if (buf->result < 0)
155 return buf->result;
156 d_ino = ino;
157 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
158 buf->result = -EOVERFLOW;
159 return -EOVERFLOW;
160 }
161 buf->result++;
162 dirent = buf->dirent;
163 if (!user_write_access_begin(dirent,
164 (unsigned long)(dirent->d_name + namlen + 1) -
165 (unsigned long)dirent))
166 goto efault;
167 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
168 unsafe_put_user(offset, &dirent->d_offset, efault_end);
169 unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
170 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
171 user_write_access_end();
172 return 0;
173 efault_end:
174 user_write_access_end();
175 efault:
176 buf->result = -EFAULT;
177 return -EFAULT;
178 }
179
SYSCALL_DEFINE3(old_readdir,unsigned int,fd,struct old_linux_dirent __user *,dirent,unsigned int,count)180 SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
181 struct old_linux_dirent __user *, dirent, unsigned int, count)
182 {
183 int error;
184 struct fd f = fdget_pos(fd);
185 struct readdir_callback buf = {
186 .ctx.actor = fillonedir,
187 .dirent = dirent
188 };
189
190 if (!f.file)
191 return -EBADF;
192
193 error = iterate_dir(f.file, &buf.ctx);
194 if (buf.result)
195 error = buf.result;
196
197 fdput_pos(f);
198 return error;
199 }
200
201 #endif /* __ARCH_WANT_OLD_READDIR */
202
203 /*
204 * New, all-improved, singing, dancing, iBCS2-compliant getdents()
205 * interface.
206 */
207 struct linux_dirent {
208 unsigned long d_ino;
209 unsigned long d_off;
210 unsigned short d_reclen;
211 char d_name[1];
212 };
213
214 struct getdents_callback {
215 struct dir_context ctx;
216 struct linux_dirent __user * current_dir;
217 int prev_reclen;
218 int count;
219 int error;
220 };
221
filldir(struct dir_context * ctx,const char * name,int namlen,loff_t offset,u64 ino,unsigned int d_type)222 static int filldir(struct dir_context *ctx, const char *name, int namlen,
223 loff_t offset, u64 ino, unsigned int d_type)
224 {
225 struct linux_dirent __user *dirent, *prev;
226 struct getdents_callback *buf =
227 container_of(ctx, struct getdents_callback, ctx);
228 unsigned long d_ino;
229 int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
230 sizeof(long));
231 int prev_reclen;
232
233 buf->error = verify_dirent_name(name, namlen);
234 if (unlikely(buf->error))
235 return buf->error;
236 buf->error = -EINVAL; /* only used if we fail.. */
237 if (reclen > buf->count)
238 return -EINVAL;
239 d_ino = ino;
240 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
241 buf->error = -EOVERFLOW;
242 return -EOVERFLOW;
243 }
244 prev_reclen = buf->prev_reclen;
245 if (prev_reclen && signal_pending(current))
246 return -EINTR;
247 dirent = buf->current_dir;
248 prev = (void __user *) dirent - prev_reclen;
249 if (!user_write_access_begin(prev, reclen + prev_reclen))
250 goto efault;
251
252 /* This might be 'dirent->d_off', but if so it will get overwritten */
253 unsafe_put_user(offset, &prev->d_off, efault_end);
254 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
255 unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
256 unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
257 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
258 user_write_access_end();
259
260 buf->current_dir = (void __user *)dirent + reclen;
261 buf->prev_reclen = reclen;
262 buf->count -= reclen;
263 return 0;
264 efault_end:
265 user_write_access_end();
266 efault:
267 buf->error = -EFAULT;
268 return -EFAULT;
269 }
270
SYSCALL_DEFINE3(getdents,unsigned int,fd,struct linux_dirent __user *,dirent,unsigned int,count)271 SYSCALL_DEFINE3(getdents, unsigned int, fd,
272 struct linux_dirent __user *, dirent, unsigned int, count)
273 {
274 struct fd f;
275 struct getdents_callback buf = {
276 .ctx.actor = filldir,
277 .count = count,
278 .current_dir = dirent
279 };
280 int error;
281
282 f = fdget_pos(fd);
283 if (!f.file)
284 return -EBADF;
285
286 error = iterate_dir(f.file, &buf.ctx);
287 if (error >= 0)
288 error = buf.error;
289 if (buf.prev_reclen) {
290 struct linux_dirent __user * lastdirent;
291 lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;
292
293 if (put_user(buf.ctx.pos, &lastdirent->d_off))
294 error = -EFAULT;
295 else
296 error = count - buf.count;
297 }
298 fdput_pos(f);
299 return error;
300 }
301
302 struct getdents_callback64 {
303 struct dir_context ctx;
304 struct linux_dirent64 __user * current_dir;
305 int prev_reclen;
306 int count;
307 int error;
308 };
309
filldir64(struct dir_context * ctx,const char * name,int namlen,loff_t offset,u64 ino,unsigned int d_type)310 static int filldir64(struct dir_context *ctx, const char *name, int namlen,
311 loff_t offset, u64 ino, unsigned int d_type)
312 {
313 struct linux_dirent64 __user *dirent, *prev;
314 struct getdents_callback64 *buf =
315 container_of(ctx, struct getdents_callback64, ctx);
316 int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
317 sizeof(u64));
318 int prev_reclen;
319
320 buf->error = verify_dirent_name(name, namlen);
321 if (unlikely(buf->error))
322 return buf->error;
323 buf->error = -EINVAL; /* only used if we fail.. */
324 if (reclen > buf->count)
325 return -EINVAL;
326 prev_reclen = buf->prev_reclen;
327 if (prev_reclen && signal_pending(current))
328 return -EINTR;
329 dirent = buf->current_dir;
330 prev = (void __user *)dirent - prev_reclen;
331 if (!user_write_access_begin(prev, reclen + prev_reclen))
332 goto efault;
333
334 /* This might be 'dirent->d_off', but if so it will get overwritten */
335 unsafe_put_user(offset, &prev->d_off, efault_end);
336 unsafe_put_user(ino, &dirent->d_ino, efault_end);
337 unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
338 unsafe_put_user(d_type, &dirent->d_type, efault_end);
339 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
340 user_write_access_end();
341
342 buf->prev_reclen = reclen;
343 buf->current_dir = (void __user *)dirent + reclen;
344 buf->count -= reclen;
345 return 0;
346
347 efault_end:
348 user_write_access_end();
349 efault:
350 buf->error = -EFAULT;
351 return -EFAULT;
352 }
353
SYSCALL_DEFINE3(getdents64,unsigned int,fd,struct linux_dirent64 __user *,dirent,unsigned int,count)354 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
355 struct linux_dirent64 __user *, dirent, unsigned int, count)
356 {
357 struct fd f;
358 struct getdents_callback64 buf = {
359 .ctx.actor = filldir64,
360 .count = count,
361 .current_dir = dirent
362 };
363 int error;
364
365 f = fdget_pos(fd);
366 if (!f.file)
367 return -EBADF;
368
369 error = iterate_dir(f.file, &buf.ctx);
370 if (error >= 0)
371 error = buf.error;
372 if (buf.prev_reclen) {
373 struct linux_dirent64 __user * lastdirent;
374 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
375
376 lastdirent = (void __user *) buf.current_dir - buf.prev_reclen;
377 if (put_user(d_off, &lastdirent->d_off))
378 error = -EFAULT;
379 else
380 error = count - buf.count;
381 }
382 fdput_pos(f);
383 return error;
384 }
385
386 #ifdef CONFIG_COMPAT
387 struct compat_old_linux_dirent {
388 compat_ulong_t d_ino;
389 compat_ulong_t d_offset;
390 unsigned short d_namlen;
391 char d_name[1];
392 };
393
394 struct compat_readdir_callback {
395 struct dir_context ctx;
396 struct compat_old_linux_dirent __user *dirent;
397 int result;
398 };
399
compat_fillonedir(struct dir_context * ctx,const char * name,int namlen,loff_t offset,u64 ino,unsigned int d_type)400 static int compat_fillonedir(struct dir_context *ctx, const char *name,
401 int namlen, loff_t offset, u64 ino,
402 unsigned int d_type)
403 {
404 struct compat_readdir_callback *buf =
405 container_of(ctx, struct compat_readdir_callback, ctx);
406 struct compat_old_linux_dirent __user *dirent;
407 compat_ulong_t d_ino;
408
409 if (buf->result)
410 return -EINVAL;
411 buf->result = verify_dirent_name(name, namlen);
412 if (buf->result < 0)
413 return buf->result;
414 d_ino = ino;
415 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
416 buf->result = -EOVERFLOW;
417 return -EOVERFLOW;
418 }
419 buf->result++;
420 dirent = buf->dirent;
421 if (!user_write_access_begin(dirent,
422 (unsigned long)(dirent->d_name + namlen + 1) -
423 (unsigned long)dirent))
424 goto efault;
425 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
426 unsafe_put_user(offset, &dirent->d_offset, efault_end);
427 unsafe_put_user(namlen, &dirent->d_namlen, efault_end);
428 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
429 user_write_access_end();
430 return 0;
431 efault_end:
432 user_write_access_end();
433 efault:
434 buf->result = -EFAULT;
435 return -EFAULT;
436 }
437
COMPAT_SYSCALL_DEFINE3(old_readdir,unsigned int,fd,struct compat_old_linux_dirent __user *,dirent,unsigned int,count)438 COMPAT_SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
439 struct compat_old_linux_dirent __user *, dirent, unsigned int, count)
440 {
441 int error;
442 struct fd f = fdget_pos(fd);
443 struct compat_readdir_callback buf = {
444 .ctx.actor = compat_fillonedir,
445 .dirent = dirent
446 };
447
448 if (!f.file)
449 return -EBADF;
450
451 error = iterate_dir(f.file, &buf.ctx);
452 if (buf.result)
453 error = buf.result;
454
455 fdput_pos(f);
456 return error;
457 }
458
459 struct compat_linux_dirent {
460 compat_ulong_t d_ino;
461 compat_ulong_t d_off;
462 unsigned short d_reclen;
463 char d_name[1];
464 };
465
466 struct compat_getdents_callback {
467 struct dir_context ctx;
468 struct compat_linux_dirent __user *current_dir;
469 int prev_reclen;
470 int count;
471 int error;
472 };
473
compat_filldir(struct dir_context * ctx,const char * name,int namlen,loff_t offset,u64 ino,unsigned int d_type)474 static int compat_filldir(struct dir_context *ctx, const char *name, int namlen,
475 loff_t offset, u64 ino, unsigned int d_type)
476 {
477 struct compat_linux_dirent __user *dirent, *prev;
478 struct compat_getdents_callback *buf =
479 container_of(ctx, struct compat_getdents_callback, ctx);
480 compat_ulong_t d_ino;
481 int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +
482 namlen + 2, sizeof(compat_long_t));
483 int prev_reclen;
484
485 buf->error = verify_dirent_name(name, namlen);
486 if (unlikely(buf->error))
487 return buf->error;
488 buf->error = -EINVAL; /* only used if we fail.. */
489 if (reclen > buf->count)
490 return -EINVAL;
491 d_ino = ino;
492 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
493 buf->error = -EOVERFLOW;
494 return -EOVERFLOW;
495 }
496 prev_reclen = buf->prev_reclen;
497 if (prev_reclen && signal_pending(current))
498 return -EINTR;
499 dirent = buf->current_dir;
500 prev = (void __user *) dirent - prev_reclen;
501 if (!user_write_access_begin(prev, reclen + prev_reclen))
502 goto efault;
503
504 unsafe_put_user(offset, &prev->d_off, efault_end);
505 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
506 unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
507 unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
508 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
509 user_write_access_end();
510
511 buf->prev_reclen = reclen;
512 buf->current_dir = (void __user *)dirent + reclen;
513 buf->count -= reclen;
514 return 0;
515 efault_end:
516 user_write_access_end();
517 efault:
518 buf->error = -EFAULT;
519 return -EFAULT;
520 }
521
COMPAT_SYSCALL_DEFINE3(getdents,unsigned int,fd,struct compat_linux_dirent __user *,dirent,unsigned int,count)522 COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd,
523 struct compat_linux_dirent __user *, dirent, unsigned int, count)
524 {
525 struct fd f;
526 struct compat_getdents_callback buf = {
527 .ctx.actor = compat_filldir,
528 .current_dir = dirent,
529 .count = count
530 };
531 int error;
532
533 f = fdget_pos(fd);
534 if (!f.file)
535 return -EBADF;
536
537 error = iterate_dir(f.file, &buf.ctx);
538 if (error >= 0)
539 error = buf.error;
540 if (buf.prev_reclen) {
541 struct compat_linux_dirent __user * lastdirent;
542 lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;
543
544 if (put_user(buf.ctx.pos, &lastdirent->d_off))
545 error = -EFAULT;
546 else
547 error = count - buf.count;
548 }
549 fdput_pos(f);
550 return error;
551 }
552 #endif
553