1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
4 * Copyright 2001-2006 Ian Kent <raven@themaw.net>
5 */
6
7 #include <linux/sched/signal.h>
8 #include "autofs_i.h"
9
10 /* We make this a static variable rather than a part of the superblock; it
11 * is better if we don't reassign numbers easily even across filesystems
12 */
13 static autofs_wqt_t autofs_next_wait_queue = 1;
14
autofs_catatonic_mode(struct autofs_sb_info * sbi)15 void autofs_catatonic_mode(struct autofs_sb_info *sbi)
16 {
17 struct autofs_wait_queue *wq, *nwq;
18
19 mutex_lock(&sbi->wq_mutex);
20 if (sbi->flags & AUTOFS_SBI_CATATONIC) {
21 mutex_unlock(&sbi->wq_mutex);
22 return;
23 }
24
25 pr_debug("entering catatonic mode\n");
26
27 sbi->flags |= AUTOFS_SBI_CATATONIC;
28 wq = sbi->queues;
29 sbi->queues = NULL; /* Erase all wait queues */
30 while (wq) {
31 nwq = wq->next;
32 wq->status = -ENOENT; /* Magic is gone - report failure */
33 kfree(wq->name.name);
34 wq->name.name = NULL;
35 wake_up_interruptible(&wq->queue);
36 if (!--wq->wait_ctr)
37 kfree(wq);
38 wq = nwq;
39 }
40 fput(sbi->pipe); /* Close the pipe */
41 sbi->pipe = NULL;
42 sbi->pipefd = -1;
43 mutex_unlock(&sbi->wq_mutex);
44 }
45
autofs_write(struct autofs_sb_info * sbi,struct file * file,const void * addr,int bytes)46 static int autofs_write(struct autofs_sb_info *sbi,
47 struct file *file, const void *addr, int bytes)
48 {
49 unsigned long sigpipe, flags;
50 const char *data = (const char *)addr;
51 ssize_t wr = 0;
52
53 sigpipe = sigismember(¤t->pending.signal, SIGPIPE);
54
55 mutex_lock(&sbi->pipe_mutex);
56 while (bytes) {
57 wr = __kernel_write(file, data, bytes, &file->f_pos);
58 if (wr <= 0)
59 break;
60 data += wr;
61 bytes -= wr;
62 }
63 mutex_unlock(&sbi->pipe_mutex);
64
65 /* Keep the currently executing process from receiving a
66 * SIGPIPE unless it was already supposed to get one
67 */
68 if (wr == -EPIPE && !sigpipe) {
69 spin_lock_irqsave(¤t->sighand->siglock, flags);
70 sigdelset(¤t->pending.signal, SIGPIPE);
71 recalc_sigpending();
72 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
73 }
74
75 /* if 'wr' returned 0 (impossible) we assume -EIO (safe) */
76 return bytes == 0 ? 0 : wr < 0 ? wr : -EIO;
77 }
78
autofs_notify_daemon(struct autofs_sb_info * sbi,struct autofs_wait_queue * wq,int type)79 static void autofs_notify_daemon(struct autofs_sb_info *sbi,
80 struct autofs_wait_queue *wq,
81 int type)
82 {
83 union {
84 struct autofs_packet_hdr hdr;
85 union autofs_packet_union v4_pkt;
86 union autofs_v5_packet_union v5_pkt;
87 } pkt;
88 struct file *pipe = NULL;
89 size_t pktsz;
90 int ret;
91
92 pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
93 (unsigned long) wq->wait_queue_token,
94 wq->name.len, wq->name.name, type);
95
96 memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
97
98 pkt.hdr.proto_version = sbi->version;
99 pkt.hdr.type = type;
100
101 switch (type) {
102 /* Kernel protocol v4 missing and expire packets */
103 case autofs_ptype_missing:
104 {
105 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
106
107 pktsz = sizeof(*mp);
108
109 mp->wait_queue_token = wq->wait_queue_token;
110 mp->len = wq->name.len;
111 memcpy(mp->name, wq->name.name, wq->name.len);
112 mp->name[wq->name.len] = '\0';
113 break;
114 }
115 case autofs_ptype_expire_multi:
116 {
117 struct autofs_packet_expire_multi *ep =
118 &pkt.v4_pkt.expire_multi;
119
120 pktsz = sizeof(*ep);
121
122 ep->wait_queue_token = wq->wait_queue_token;
123 ep->len = wq->name.len;
124 memcpy(ep->name, wq->name.name, wq->name.len);
125 ep->name[wq->name.len] = '\0';
126 break;
127 }
128 /*
129 * Kernel protocol v5 packet for handling indirect and direct
130 * mount missing and expire requests
131 */
132 case autofs_ptype_missing_indirect:
133 case autofs_ptype_expire_indirect:
134 case autofs_ptype_missing_direct:
135 case autofs_ptype_expire_direct:
136 {
137 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
138 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
139
140 pktsz = sizeof(*packet);
141
142 packet->wait_queue_token = wq->wait_queue_token;
143 packet->len = wq->name.len;
144 memcpy(packet->name, wq->name.name, wq->name.len);
145 packet->name[wq->name.len] = '\0';
146 packet->dev = wq->dev;
147 packet->ino = wq->ino;
148 packet->uid = from_kuid_munged(user_ns, wq->uid);
149 packet->gid = from_kgid_munged(user_ns, wq->gid);
150 packet->pid = wq->pid;
151 packet->tgid = wq->tgid;
152 break;
153 }
154 default:
155 pr_warn("bad type %d!\n", type);
156 mutex_unlock(&sbi->wq_mutex);
157 return;
158 }
159
160 pipe = get_file(sbi->pipe);
161
162 mutex_unlock(&sbi->wq_mutex);
163
164 switch (ret = autofs_write(sbi, pipe, &pkt, pktsz)) {
165 case 0:
166 break;
167 case -ENOMEM:
168 case -ERESTARTSYS:
169 /* Just fail this one */
170 autofs_wait_release(sbi, wq->wait_queue_token, ret);
171 break;
172 default:
173 autofs_catatonic_mode(sbi);
174 break;
175 }
176 fput(pipe);
177 }
178
autofs_getpath(struct autofs_sb_info * sbi,struct dentry * dentry,char * name)179 static int autofs_getpath(struct autofs_sb_info *sbi,
180 struct dentry *dentry, char *name)
181 {
182 struct dentry *root = sbi->sb->s_root;
183 struct dentry *tmp;
184 char *buf;
185 char *p;
186 int len;
187 unsigned seq;
188
189 rename_retry:
190 buf = name;
191 len = 0;
192
193 seq = read_seqbegin(&rename_lock);
194 rcu_read_lock();
195 spin_lock(&sbi->fs_lock);
196 for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
197 len += tmp->d_name.len + 1;
198
199 if (!len || --len > NAME_MAX) {
200 spin_unlock(&sbi->fs_lock);
201 rcu_read_unlock();
202 if (read_seqretry(&rename_lock, seq))
203 goto rename_retry;
204 return 0;
205 }
206
207 *(buf + len) = '\0';
208 p = buf + len - dentry->d_name.len;
209 strncpy(p, dentry->d_name.name, dentry->d_name.len);
210
211 for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
212 *(--p) = '/';
213 p -= tmp->d_name.len;
214 strncpy(p, tmp->d_name.name, tmp->d_name.len);
215 }
216 spin_unlock(&sbi->fs_lock);
217 rcu_read_unlock();
218 if (read_seqretry(&rename_lock, seq))
219 goto rename_retry;
220
221 return len;
222 }
223
224 static struct autofs_wait_queue *
autofs_find_wait(struct autofs_sb_info * sbi,const struct qstr * qstr)225 autofs_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
226 {
227 struct autofs_wait_queue *wq;
228
229 for (wq = sbi->queues; wq; wq = wq->next) {
230 if (wq->name.hash == qstr->hash &&
231 wq->name.len == qstr->len &&
232 wq->name.name &&
233 !memcmp(wq->name.name, qstr->name, qstr->len))
234 break;
235 }
236 return wq;
237 }
238
239 /*
240 * Check if we have a valid request.
241 * Returns
242 * 1 if the request should continue.
243 * In this case we can return an autofs_wait_queue entry if one is
244 * found or NULL to idicate a new wait needs to be created.
245 * 0 or a negative errno if the request shouldn't continue.
246 */
validate_request(struct autofs_wait_queue ** wait,struct autofs_sb_info * sbi,const struct qstr * qstr,const struct path * path,enum autofs_notify notify)247 static int validate_request(struct autofs_wait_queue **wait,
248 struct autofs_sb_info *sbi,
249 const struct qstr *qstr,
250 const struct path *path, enum autofs_notify notify)
251 {
252 struct dentry *dentry = path->dentry;
253 struct autofs_wait_queue *wq;
254 struct autofs_info *ino;
255
256 if (sbi->flags & AUTOFS_SBI_CATATONIC)
257 return -ENOENT;
258
259 /* Wait in progress, continue; */
260 wq = autofs_find_wait(sbi, qstr);
261 if (wq) {
262 *wait = wq;
263 return 1;
264 }
265
266 *wait = NULL;
267
268 /* If we don't yet have any info this is a new request */
269 ino = autofs_dentry_ino(dentry);
270 if (!ino)
271 return 1;
272
273 /*
274 * If we've been asked to wait on an existing expire (NFY_NONE)
275 * but there is no wait in the queue ...
276 */
277 if (notify == NFY_NONE) {
278 /*
279 * Either we've betean the pending expire to post it's
280 * wait or it finished while we waited on the mutex.
281 * So we need to wait till either, the wait appears
282 * or the expire finishes.
283 */
284
285 while (ino->flags & AUTOFS_INF_EXPIRING) {
286 mutex_unlock(&sbi->wq_mutex);
287 schedule_timeout_interruptible(HZ/10);
288 if (mutex_lock_interruptible(&sbi->wq_mutex))
289 return -EINTR;
290
291 if (sbi->flags & AUTOFS_SBI_CATATONIC)
292 return -ENOENT;
293
294 wq = autofs_find_wait(sbi, qstr);
295 if (wq) {
296 *wait = wq;
297 return 1;
298 }
299 }
300
301 /*
302 * Not ideal but the status has already gone. Of the two
303 * cases where we wait on NFY_NONE neither depend on the
304 * return status of the wait.
305 */
306 return 0;
307 }
308
309 /*
310 * If we've been asked to trigger a mount and the request
311 * completed while we waited on the mutex ...
312 */
313 if (notify == NFY_MOUNT) {
314 struct dentry *new = NULL;
315 struct path this;
316 int valid = 1;
317
318 /*
319 * If the dentry was successfully mounted while we slept
320 * on the wait queue mutex we can return success. If it
321 * isn't mounted (doesn't have submounts for the case of
322 * a multi-mount with no mount at it's base) we can
323 * continue on and create a new request.
324 */
325 if (!IS_ROOT(dentry)) {
326 if (d_unhashed(dentry) &&
327 d_really_is_positive(dentry)) {
328 struct dentry *parent = dentry->d_parent;
329
330 new = d_lookup(parent, &dentry->d_name);
331 if (new)
332 dentry = new;
333 }
334 }
335 this.mnt = path->mnt;
336 this.dentry = dentry;
337 if (path_has_submounts(&this))
338 valid = 0;
339
340 if (new)
341 dput(new);
342 return valid;
343 }
344
345 return 1;
346 }
347
autofs_wait(struct autofs_sb_info * sbi,const struct path * path,enum autofs_notify notify)348 int autofs_wait(struct autofs_sb_info *sbi,
349 const struct path *path, enum autofs_notify notify)
350 {
351 struct dentry *dentry = path->dentry;
352 struct autofs_wait_queue *wq;
353 struct qstr qstr;
354 char *name;
355 int status, ret, type;
356 pid_t pid;
357 pid_t tgid;
358
359 /* In catatonic mode, we don't wait for nobody */
360 if (sbi->flags & AUTOFS_SBI_CATATONIC)
361 return -ENOENT;
362
363 /*
364 * Try translating pids to the namespace of the daemon.
365 *
366 * Zero means failure: we are in an unrelated pid namespace.
367 */
368 pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
369 tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
370 if (pid == 0 || tgid == 0)
371 return -ENOENT;
372
373 if (d_really_is_negative(dentry)) {
374 /*
375 * A wait for a negative dentry is invalid for certain
376 * cases. A direct or offset mount "always" has its mount
377 * point directory created and so the request dentry must
378 * be positive or the map key doesn't exist. The situation
379 * is very similar for indirect mounts except only dentrys
380 * in the root of the autofs file system may be negative.
381 */
382 if (autofs_type_trigger(sbi->type))
383 return -ENOENT;
384 else if (!IS_ROOT(dentry->d_parent))
385 return -ENOENT;
386 }
387
388 name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
389 if (!name)
390 return -ENOMEM;
391
392 /* If this is a direct mount request create a dummy name */
393 if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
394 qstr.len = sprintf(name, "%p", dentry);
395 else {
396 qstr.len = autofs_getpath(sbi, dentry, name);
397 if (!qstr.len) {
398 kfree(name);
399 return -ENOENT;
400 }
401 }
402 qstr.name = name;
403 qstr.hash = full_name_hash(dentry, name, qstr.len);
404
405 if (mutex_lock_interruptible(&sbi->wq_mutex)) {
406 kfree(qstr.name);
407 return -EINTR;
408 }
409
410 ret = validate_request(&wq, sbi, &qstr, path, notify);
411 if (ret <= 0) {
412 if (ret != -EINTR)
413 mutex_unlock(&sbi->wq_mutex);
414 kfree(qstr.name);
415 return ret;
416 }
417
418 if (!wq) {
419 /* Create a new wait queue */
420 wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
421 if (!wq) {
422 kfree(qstr.name);
423 mutex_unlock(&sbi->wq_mutex);
424 return -ENOMEM;
425 }
426
427 wq->wait_queue_token = autofs_next_wait_queue;
428 if (++autofs_next_wait_queue == 0)
429 autofs_next_wait_queue = 1;
430 wq->next = sbi->queues;
431 sbi->queues = wq;
432 init_waitqueue_head(&wq->queue);
433 memcpy(&wq->name, &qstr, sizeof(struct qstr));
434 wq->dev = autofs_get_dev(sbi);
435 wq->ino = autofs_get_ino(sbi);
436 wq->uid = current_uid();
437 wq->gid = current_gid();
438 wq->pid = pid;
439 wq->tgid = tgid;
440 wq->status = -EINTR; /* Status return if interrupted */
441 wq->wait_ctr = 2;
442
443 if (sbi->version < 5) {
444 if (notify == NFY_MOUNT)
445 type = autofs_ptype_missing;
446 else
447 type = autofs_ptype_expire_multi;
448 } else {
449 if (notify == NFY_MOUNT)
450 type = autofs_type_trigger(sbi->type) ?
451 autofs_ptype_missing_direct :
452 autofs_ptype_missing_indirect;
453 else
454 type = autofs_type_trigger(sbi->type) ?
455 autofs_ptype_expire_direct :
456 autofs_ptype_expire_indirect;
457 }
458
459 pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
460 (unsigned long) wq->wait_queue_token, wq->name.len,
461 wq->name.name, notify);
462
463 /*
464 * autofs_notify_daemon() may block; it will unlock ->wq_mutex
465 */
466 autofs_notify_daemon(sbi, wq, type);
467 } else {
468 wq->wait_ctr++;
469 pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
470 (unsigned long) wq->wait_queue_token, wq->name.len,
471 wq->name.name, notify);
472 mutex_unlock(&sbi->wq_mutex);
473 kfree(qstr.name);
474 }
475
476 /*
477 * wq->name.name is NULL iff the lock is already released
478 * or the mount has been made catatonic.
479 */
480 wait_event_killable(wq->queue, wq->name.name == NULL);
481 status = wq->status;
482
483 /*
484 * For direct and offset mounts we need to track the requester's
485 * uid and gid in the dentry info struct. This is so it can be
486 * supplied, on request, by the misc device ioctl interface.
487 * This is needed during daemon resatart when reconnecting
488 * to existing, active, autofs mounts. The uid and gid (and
489 * related string values) may be used for macro substitution
490 * in autofs mount maps.
491 */
492 if (!status) {
493 struct autofs_info *ino;
494 struct dentry *de = NULL;
495
496 /* direct mount or browsable map */
497 ino = autofs_dentry_ino(dentry);
498 if (!ino) {
499 /* If not lookup actual dentry used */
500 de = d_lookup(dentry->d_parent, &dentry->d_name);
501 if (de)
502 ino = autofs_dentry_ino(de);
503 }
504
505 /* Set mount requester */
506 if (ino) {
507 spin_lock(&sbi->fs_lock);
508 ino->uid = wq->uid;
509 ino->gid = wq->gid;
510 spin_unlock(&sbi->fs_lock);
511 }
512
513 if (de)
514 dput(de);
515 }
516
517 /* Are we the last process to need status? */
518 mutex_lock(&sbi->wq_mutex);
519 if (!--wq->wait_ctr)
520 kfree(wq);
521 mutex_unlock(&sbi->wq_mutex);
522
523 return status;
524 }
525
526
autofs_wait_release(struct autofs_sb_info * sbi,autofs_wqt_t wait_queue_token,int status)527 int autofs_wait_release(struct autofs_sb_info *sbi,
528 autofs_wqt_t wait_queue_token, int status)
529 {
530 struct autofs_wait_queue *wq, **wql;
531
532 mutex_lock(&sbi->wq_mutex);
533 for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
534 if (wq->wait_queue_token == wait_queue_token)
535 break;
536 }
537
538 if (!wq) {
539 mutex_unlock(&sbi->wq_mutex);
540 return -EINVAL;
541 }
542
543 *wql = wq->next; /* Unlink from chain */
544 kfree(wq->name.name);
545 wq->name.name = NULL; /* Do not wait on this queue */
546 wq->status = status;
547 wake_up(&wq->queue);
548 if (!--wq->wait_ctr)
549 kfree(wq);
550 mutex_unlock(&sbi->wq_mutex);
551
552 return 0;
553 }
554