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 | * Some filesystems were never converted to '->iterate_shared()' |
29 | * and their directory iterators want the inode lock held for |
30 | * writing. This wrapper allows for converting from the shared |
31 | * semantics to the exclusive inode use. |
32 | */ |
33 | int wrap_directory_iterator(struct file *file, |
34 | struct dir_context *ctx, |
35 | int (*iter)(struct file *, struct dir_context *)) |
36 | { |
37 | struct inode *inode = file_inode(f: file); |
38 | int ret; |
39 | |
40 | /* |
41 | * We'd love to have an 'inode_upgrade_trylock()' operation, |
42 | * see the comment in mmap_upgrade_trylock() in mm/memory.c. |
43 | * |
44 | * But considering this is for "filesystems that never got |
45 | * converted", it really doesn't matter. |
46 | * |
47 | * Also note that since we have to return with the lock held |
48 | * for reading, we can't use the "killable()" locking here, |
49 | * since we do need to get the lock even if we're dying. |
50 | * |
51 | * We could do the write part killably and then get the read |
52 | * lock unconditionally if it mattered, but see above on why |
53 | * this does the very simplistic conversion. |
54 | */ |
55 | up_read(sem: &inode->i_rwsem); |
56 | down_write(sem: &inode->i_rwsem); |
57 | |
58 | /* |
59 | * Since we dropped the inode lock, we should do the |
60 | * DEADDIR test again. See 'iterate_dir()' below. |
61 | * |
62 | * Note that we don't need to re-do the f_pos games, |
63 | * since the file must be locked wrt f_pos anyway. |
64 | */ |
65 | ret = -ENOENT; |
66 | if (!IS_DEADDIR(inode)) |
67 | ret = iter(file, ctx); |
68 | |
69 | downgrade_write(sem: &inode->i_rwsem); |
70 | return ret; |
71 | } |
72 | EXPORT_SYMBOL(wrap_directory_iterator); |
73 | |
74 | /* |
75 | * Note the "unsafe_put_user() semantics: we goto a |
76 | * label for errors. |
77 | */ |
78 | #define unsafe_copy_dirent_name(_dst, _src, _len, label) do { \ |
79 | char __user *dst = (_dst); \ |
80 | const char *src = (_src); \ |
81 | size_t len = (_len); \ |
82 | unsafe_put_user(0, dst+len, label); \ |
83 | unsafe_copy_to_user(dst, src, len, label); \ |
84 | } while (0) |
85 | |
86 | |
87 | int iterate_dir(struct file *file, struct dir_context *ctx) |
88 | { |
89 | struct inode *inode = file_inode(f: file); |
90 | int res = -ENOTDIR; |
91 | |
92 | if (!file->f_op->iterate_shared) |
93 | goto out; |
94 | |
95 | res = security_file_permission(file, MAY_READ); |
96 | if (res) |
97 | goto out; |
98 | |
99 | res = down_read_killable(sem: &inode->i_rwsem); |
100 | if (res) |
101 | goto out; |
102 | |
103 | res = -ENOENT; |
104 | if (!IS_DEADDIR(inode)) { |
105 | ctx->pos = file->f_pos; |
106 | res = file->f_op->iterate_shared(file, ctx); |
107 | file->f_pos = ctx->pos; |
108 | fsnotify_access(file); |
109 | file_accessed(file); |
110 | } |
111 | inode_unlock_shared(inode); |
112 | out: |
113 | return res; |
114 | } |
115 | EXPORT_SYMBOL(iterate_dir); |
116 | |
117 | /* |
118 | * POSIX says that a dirent name cannot contain NULL or a '/'. |
119 | * |
120 | * It's not 100% clear what we should really do in this case. |
121 | * The filesystem is clearly corrupted, but returning a hard |
122 | * error means that you now don't see any of the other names |
123 | * either, so that isn't a perfect alternative. |
124 | * |
125 | * And if you return an error, what error do you use? Several |
126 | * filesystems seem to have decided on EUCLEAN being the error |
127 | * code for EFSCORRUPTED, and that may be the error to use. Or |
128 | * just EIO, which is perhaps more obvious to users. |
129 | * |
130 | * In order to see the other file names in the directory, the |
131 | * caller might want to make this a "soft" error: skip the |
132 | * entry, and return the error at the end instead. |
133 | * |
134 | * Note that this should likely do a "memchr(name, 0, len)" |
135 | * check too, since that would be filesystem corruption as |
136 | * well. However, that case can't actually confuse user space, |
137 | * which has to do a strlen() on the name anyway to find the |
138 | * filename length, and the above "soft error" worry means |
139 | * that it's probably better left alone until we have that |
140 | * issue clarified. |
141 | * |
142 | * Note the PATH_MAX check - it's arbitrary but the real |
143 | * kernel limit on a possible path component, not NAME_MAX, |
144 | * which is the technical standard limit. |
145 | */ |
146 | static int verify_dirent_name(const char *name, int len) |
147 | { |
148 | if (len <= 0 || len >= PATH_MAX) |
149 | return -EIO; |
150 | if (memchr(p: name, c: '/', size: len)) |
151 | return -EIO; |
152 | return 0; |
153 | } |
154 | |
155 | /* |
156 | * Traditional linux readdir() handling.. |
157 | * |
158 | * "count=1" is a special case, meaning that the buffer is one |
159 | * dirent-structure in size and that the code can't handle more |
160 | * anyway. Thus the special "fillonedir()" function for that |
161 | * case (the low-level handlers don't need to care about this). |
162 | */ |
163 | |
164 | #ifdef __ARCH_WANT_OLD_READDIR |
165 | |
166 | struct old_linux_dirent { |
167 | unsigned long d_ino; |
168 | unsigned long d_offset; |
169 | unsigned short d_namlen; |
170 | char d_name[]; |
171 | }; |
172 | |
173 | struct readdir_callback { |
174 | struct dir_context ctx; |
175 | struct old_linux_dirent __user * dirent; |
176 | int result; |
177 | }; |
178 | |
179 | static bool fillonedir(struct dir_context *ctx, const char *name, int namlen, |
180 | loff_t offset, u64 ino, unsigned int d_type) |
181 | { |
182 | struct readdir_callback *buf = |
183 | container_of(ctx, struct readdir_callback, ctx); |
184 | struct old_linux_dirent __user * dirent; |
185 | unsigned long d_ino; |
186 | |
187 | if (buf->result) |
188 | return false; |
189 | buf->result = verify_dirent_name(name, len: namlen); |
190 | if (buf->result) |
191 | return false; |
192 | d_ino = ino; |
193 | if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) { |
194 | buf->result = -EOVERFLOW; |
195 | return false; |
196 | } |
197 | buf->result++; |
198 | dirent = buf->dirent; |
199 | if (!user_write_access_begin(dirent, |
200 | (unsigned long)(dirent->d_name + namlen + 1) - |
201 | (unsigned long)dirent)) |
202 | goto efault; |
203 | unsafe_put_user(d_ino, &dirent->d_ino, efault_end); |
204 | unsafe_put_user(offset, &dirent->d_offset, efault_end); |
205 | unsafe_put_user(namlen, &dirent->d_namlen, efault_end); |
206 | unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end); |
207 | user_write_access_end(); |
208 | return true; |
209 | efault_end: |
210 | user_write_access_end(); |
211 | efault: |
212 | buf->result = -EFAULT; |
213 | return false; |
214 | } |
215 | |
216 | SYSCALL_DEFINE3(old_readdir, unsigned int, fd, |
217 | struct old_linux_dirent __user *, dirent, unsigned int, count) |
218 | { |
219 | int error; |
220 | struct fd f = fdget_pos(fd); |
221 | struct readdir_callback buf = { |
222 | .ctx.actor = fillonedir, |
223 | .dirent = dirent |
224 | }; |
225 | |
226 | if (!f.file) |
227 | return -EBADF; |
228 | |
229 | error = iterate_dir(f.file, &buf.ctx); |
230 | if (buf.result) |
231 | error = buf.result; |
232 | |
233 | fdput_pos(f); |
234 | return error; |
235 | } |
236 | |
237 | #endif /* __ARCH_WANT_OLD_READDIR */ |
238 | |
239 | /* |
240 | * New, all-improved, singing, dancing, iBCS2-compliant getdents() |
241 | * interface. |
242 | */ |
243 | struct linux_dirent { |
244 | unsigned long d_ino; |
245 | unsigned long d_off; |
246 | unsigned short d_reclen; |
247 | char d_name[]; |
248 | }; |
249 | |
250 | struct getdents_callback { |
251 | struct dir_context ctx; |
252 | struct linux_dirent __user * current_dir; |
253 | int prev_reclen; |
254 | int count; |
255 | int error; |
256 | }; |
257 | |
258 | static bool filldir(struct dir_context *ctx, const char *name, int namlen, |
259 | loff_t offset, u64 ino, unsigned int d_type) |
260 | { |
261 | struct linux_dirent __user *dirent, *prev; |
262 | struct getdents_callback *buf = |
263 | container_of(ctx, struct getdents_callback, ctx); |
264 | unsigned long d_ino; |
265 | int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2, |
266 | sizeof(long)); |
267 | int prev_reclen; |
268 | |
269 | buf->error = verify_dirent_name(name, len: namlen); |
270 | if (unlikely(buf->error)) |
271 | return false; |
272 | buf->error = -EINVAL; /* only used if we fail.. */ |
273 | if (reclen > buf->count) |
274 | return false; |
275 | d_ino = ino; |
276 | if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) { |
277 | buf->error = -EOVERFLOW; |
278 | return false; |
279 | } |
280 | prev_reclen = buf->prev_reclen; |
281 | if (prev_reclen && signal_pending(current)) |
282 | return false; |
283 | dirent = buf->current_dir; |
284 | prev = (void __user *) dirent - prev_reclen; |
285 | if (!user_write_access_begin(prev, reclen + prev_reclen)) |
286 | goto efault; |
287 | |
288 | /* This might be 'dirent->d_off', but if so it will get overwritten */ |
289 | unsafe_put_user(offset, &prev->d_off, efault_end); |
290 | unsafe_put_user(d_ino, &dirent->d_ino, efault_end); |
291 | unsafe_put_user(reclen, &dirent->d_reclen, efault_end); |
292 | unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end); |
293 | unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end); |
294 | user_write_access_end(); |
295 | |
296 | buf->current_dir = (void __user *)dirent + reclen; |
297 | buf->prev_reclen = reclen; |
298 | buf->count -= reclen; |
299 | return true; |
300 | efault_end: |
301 | user_write_access_end(); |
302 | efault: |
303 | buf->error = -EFAULT; |
304 | return false; |
305 | } |
306 | |
307 | SYSCALL_DEFINE3(getdents, unsigned int, fd, |
308 | struct linux_dirent __user *, dirent, unsigned int, count) |
309 | { |
310 | struct fd f; |
311 | struct getdents_callback buf = { |
312 | .ctx.actor = filldir, |
313 | .count = count, |
314 | .current_dir = dirent |
315 | }; |
316 | int error; |
317 | |
318 | f = fdget_pos(fd); |
319 | if (!f.file) |
320 | return -EBADF; |
321 | |
322 | error = iterate_dir(f.file, &buf.ctx); |
323 | if (error >= 0) |
324 | error = buf.error; |
325 | if (buf.prev_reclen) { |
326 | struct linux_dirent __user * lastdirent; |
327 | lastdirent = (void __user *)buf.current_dir - buf.prev_reclen; |
328 | |
329 | if (put_user(buf.ctx.pos, &lastdirent->d_off)) |
330 | error = -EFAULT; |
331 | else |
332 | error = count - buf.count; |
333 | } |
334 | fdput_pos(f); |
335 | return error; |
336 | } |
337 | |
338 | struct getdents_callback64 { |
339 | struct dir_context ctx; |
340 | struct linux_dirent64 __user * current_dir; |
341 | int prev_reclen; |
342 | int count; |
343 | int error; |
344 | }; |
345 | |
346 | static bool filldir64(struct dir_context *ctx, const char *name, int namlen, |
347 | loff_t offset, u64 ino, unsigned int d_type) |
348 | { |
349 | struct linux_dirent64 __user *dirent, *prev; |
350 | struct getdents_callback64 *buf = |
351 | container_of(ctx, struct getdents_callback64, ctx); |
352 | int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1, |
353 | sizeof(u64)); |
354 | int prev_reclen; |
355 | |
356 | buf->error = verify_dirent_name(name, len: namlen); |
357 | if (unlikely(buf->error)) |
358 | return false; |
359 | buf->error = -EINVAL; /* only used if we fail.. */ |
360 | if (reclen > buf->count) |
361 | return false; |
362 | prev_reclen = buf->prev_reclen; |
363 | if (prev_reclen && signal_pending(current)) |
364 | return false; |
365 | dirent = buf->current_dir; |
366 | prev = (void __user *)dirent - prev_reclen; |
367 | if (!user_write_access_begin(prev, reclen + prev_reclen)) |
368 | goto efault; |
369 | |
370 | /* This might be 'dirent->d_off', but if so it will get overwritten */ |
371 | unsafe_put_user(offset, &prev->d_off, efault_end); |
372 | unsafe_put_user(ino, &dirent->d_ino, efault_end); |
373 | unsafe_put_user(reclen, &dirent->d_reclen, efault_end); |
374 | unsafe_put_user(d_type, &dirent->d_type, efault_end); |
375 | unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end); |
376 | user_write_access_end(); |
377 | |
378 | buf->prev_reclen = reclen; |
379 | buf->current_dir = (void __user *)dirent + reclen; |
380 | buf->count -= reclen; |
381 | return true; |
382 | |
383 | efault_end: |
384 | user_write_access_end(); |
385 | efault: |
386 | buf->error = -EFAULT; |
387 | return false; |
388 | } |
389 | |
390 | SYSCALL_DEFINE3(getdents64, unsigned int, fd, |
391 | struct linux_dirent64 __user *, dirent, unsigned int, count) |
392 | { |
393 | struct fd f; |
394 | struct getdents_callback64 buf = { |
395 | .ctx.actor = filldir64, |
396 | .count = count, |
397 | .current_dir = dirent |
398 | }; |
399 | int error; |
400 | |
401 | f = fdget_pos(fd); |
402 | if (!f.file) |
403 | return -EBADF; |
404 | |
405 | error = iterate_dir(f.file, &buf.ctx); |
406 | if (error >= 0) |
407 | error = buf.error; |
408 | if (buf.prev_reclen) { |
409 | struct linux_dirent64 __user * lastdirent; |
410 | typeof(lastdirent->d_off) d_off = buf.ctx.pos; |
411 | |
412 | lastdirent = (void __user *) buf.current_dir - buf.prev_reclen; |
413 | if (put_user(d_off, &lastdirent->d_off)) |
414 | error = -EFAULT; |
415 | else |
416 | error = count - buf.count; |
417 | } |
418 | fdput_pos(f); |
419 | return error; |
420 | } |
421 | |
422 | #ifdef CONFIG_COMPAT |
423 | struct compat_old_linux_dirent { |
424 | compat_ulong_t d_ino; |
425 | compat_ulong_t d_offset; |
426 | unsigned short d_namlen; |
427 | char d_name[]; |
428 | }; |
429 | |
430 | struct compat_readdir_callback { |
431 | struct dir_context ctx; |
432 | struct compat_old_linux_dirent __user *dirent; |
433 | int result; |
434 | }; |
435 | |
436 | static bool compat_fillonedir(struct dir_context *ctx, const char *name, |
437 | int namlen, loff_t offset, u64 ino, |
438 | unsigned int d_type) |
439 | { |
440 | struct compat_readdir_callback *buf = |
441 | container_of(ctx, struct compat_readdir_callback, ctx); |
442 | struct compat_old_linux_dirent __user *dirent; |
443 | compat_ulong_t d_ino; |
444 | |
445 | if (buf->result) |
446 | return false; |
447 | buf->result = verify_dirent_name(name, len: namlen); |
448 | if (buf->result) |
449 | return false; |
450 | d_ino = ino; |
451 | if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) { |
452 | buf->result = -EOVERFLOW; |
453 | return false; |
454 | } |
455 | buf->result++; |
456 | dirent = buf->dirent; |
457 | if (!user_write_access_begin(dirent, |
458 | (unsigned long)(dirent->d_name + namlen + 1) - |
459 | (unsigned long)dirent)) |
460 | goto efault; |
461 | unsafe_put_user(d_ino, &dirent->d_ino, efault_end); |
462 | unsafe_put_user(offset, &dirent->d_offset, efault_end); |
463 | unsafe_put_user(namlen, &dirent->d_namlen, efault_end); |
464 | unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end); |
465 | user_write_access_end(); |
466 | return true; |
467 | efault_end: |
468 | user_write_access_end(); |
469 | efault: |
470 | buf->result = -EFAULT; |
471 | return false; |
472 | } |
473 | |
474 | COMPAT_SYSCALL_DEFINE3(old_readdir, unsigned int, fd, |
475 | struct compat_old_linux_dirent __user *, dirent, unsigned int, count) |
476 | { |
477 | int error; |
478 | struct fd f = fdget_pos(fd); |
479 | struct compat_readdir_callback buf = { |
480 | .ctx.actor = compat_fillonedir, |
481 | .dirent = dirent |
482 | }; |
483 | |
484 | if (!f.file) |
485 | return -EBADF; |
486 | |
487 | error = iterate_dir(f.file, &buf.ctx); |
488 | if (buf.result) |
489 | error = buf.result; |
490 | |
491 | fdput_pos(f); |
492 | return error; |
493 | } |
494 | |
495 | struct compat_linux_dirent { |
496 | compat_ulong_t d_ino; |
497 | compat_ulong_t d_off; |
498 | unsigned short d_reclen; |
499 | char d_name[]; |
500 | }; |
501 | |
502 | struct compat_getdents_callback { |
503 | struct dir_context ctx; |
504 | struct compat_linux_dirent __user *current_dir; |
505 | int prev_reclen; |
506 | int count; |
507 | int error; |
508 | }; |
509 | |
510 | static bool compat_filldir(struct dir_context *ctx, const char *name, int namlen, |
511 | loff_t offset, u64 ino, unsigned int d_type) |
512 | { |
513 | struct compat_linux_dirent __user *dirent, *prev; |
514 | struct compat_getdents_callback *buf = |
515 | container_of(ctx, struct compat_getdents_callback, ctx); |
516 | compat_ulong_t d_ino; |
517 | int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) + |
518 | namlen + 2, sizeof(compat_long_t)); |
519 | int prev_reclen; |
520 | |
521 | buf->error = verify_dirent_name(name, len: namlen); |
522 | if (unlikely(buf->error)) |
523 | return false; |
524 | buf->error = -EINVAL; /* only used if we fail.. */ |
525 | if (reclen > buf->count) |
526 | return false; |
527 | d_ino = ino; |
528 | if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) { |
529 | buf->error = -EOVERFLOW; |
530 | return false; |
531 | } |
532 | prev_reclen = buf->prev_reclen; |
533 | if (prev_reclen && signal_pending(current)) |
534 | return false; |
535 | dirent = buf->current_dir; |
536 | prev = (void __user *) dirent - prev_reclen; |
537 | if (!user_write_access_begin(prev, reclen + prev_reclen)) |
538 | goto efault; |
539 | |
540 | unsafe_put_user(offset, &prev->d_off, efault_end); |
541 | unsafe_put_user(d_ino, &dirent->d_ino, efault_end); |
542 | unsafe_put_user(reclen, &dirent->d_reclen, efault_end); |
543 | unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end); |
544 | unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end); |
545 | user_write_access_end(); |
546 | |
547 | buf->prev_reclen = reclen; |
548 | buf->current_dir = (void __user *)dirent + reclen; |
549 | buf->count -= reclen; |
550 | return true; |
551 | efault_end: |
552 | user_write_access_end(); |
553 | efault: |
554 | buf->error = -EFAULT; |
555 | return false; |
556 | } |
557 | |
558 | COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd, |
559 | struct compat_linux_dirent __user *, dirent, unsigned int, count) |
560 | { |
561 | struct fd f; |
562 | struct compat_getdents_callback buf = { |
563 | .ctx.actor = compat_filldir, |
564 | .current_dir = dirent, |
565 | .count = count |
566 | }; |
567 | int error; |
568 | |
569 | f = fdget_pos(fd); |
570 | if (!f.file) |
571 | return -EBADF; |
572 | |
573 | error = iterate_dir(f.file, &buf.ctx); |
574 | if (error >= 0) |
575 | error = buf.error; |
576 | if (buf.prev_reclen) { |
577 | struct compat_linux_dirent __user * lastdirent; |
578 | lastdirent = (void __user *)buf.current_dir - buf.prev_reclen; |
579 | |
580 | if (put_user(buf.ctx.pos, &lastdirent->d_off)) |
581 | error = -EFAULT; |
582 | else |
583 | error = count - buf.count; |
584 | } |
585 | fdput_pos(f); |
586 | return error; |
587 | } |
588 | #endif |
589 | |