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Linux/fs/autofs4/waitq.c

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  1 /*
  2  * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
  3  * Copyright 2001-2006 Ian Kent <raven@themaw.net>
  4  *
  5  * This file is part of the Linux kernel and is made available under
  6  * the terms of the GNU General Public License, version 2, or at your
  7  * option, any later version, incorporated herein by reference.
  8  */
  9 
 10 #include <linux/slab.h>
 11 #include <linux/time.h>
 12 #include <linux/signal.h>
 13 #include <linux/sched/signal.h>
 14 #include <linux/file.h>
 15 #include "autofs_i.h"
 16 
 17 /* We make this a static variable rather than a part of the superblock; it
 18  * is better if we don't reassign numbers easily even across filesystems
 19  */
 20 static autofs_wqt_t autofs4_next_wait_queue = 1;
 21 
 22 /* These are the signals we allow interrupting a pending mount */
 23 #define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
 24 
 25 void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
 26 {
 27         struct autofs_wait_queue *wq, *nwq;
 28 
 29         mutex_lock(&sbi->wq_mutex);
 30         if (sbi->catatonic) {
 31                 mutex_unlock(&sbi->wq_mutex);
 32                 return;
 33         }
 34 
 35         pr_debug("entering catatonic mode\n");
 36 
 37         sbi->catatonic = 1;
 38         wq = sbi->queues;
 39         sbi->queues = NULL;     /* Erase all wait queues */
 40         while (wq) {
 41                 nwq = wq->next;
 42                 wq->status = -ENOENT; /* Magic is gone - report failure */
 43                 kfree(wq->name.name);
 44                 wq->name.name = NULL;
 45                 wq->wait_ctr--;
 46                 wake_up_interruptible(&wq->queue);
 47                 wq = nwq;
 48         }
 49         fput(sbi->pipe);        /* Close the pipe */
 50         sbi->pipe = NULL;
 51         sbi->pipefd = -1;
 52         mutex_unlock(&sbi->wq_mutex);
 53 }
 54 
 55 static int autofs4_write(struct autofs_sb_info *sbi,
 56                          struct file *file, const void *addr, int bytes)
 57 {
 58         unsigned long sigpipe, flags;
 59         const char *data = (const char *)addr;
 60         ssize_t wr = 0;
 61 
 62         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
 63 
 64         mutex_lock(&sbi->pipe_mutex);
 65         while (bytes) {
 66                 wr = __kernel_write(file, data, bytes, &file->f_pos);
 67                 if (wr <= 0)
 68                         break;
 69                 data += wr;
 70                 bytes -= wr;
 71         }
 72         mutex_unlock(&sbi->pipe_mutex);
 73 
 74         /* Keep the currently executing process from receiving a
 75          * SIGPIPE unless it was already supposed to get one
 76          */
 77         if (wr == -EPIPE && !sigpipe) {
 78                 spin_lock_irqsave(&current->sighand->siglock, flags);
 79                 sigdelset(&current->pending.signal, SIGPIPE);
 80                 recalc_sigpending();
 81                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
 82         }
 83 
 84         /* if 'wr' returned 0 (impossible) we assume -EIO (safe) */
 85         return bytes == 0 ? 0 : wr < 0 ? wr : -EIO;
 86 }
 87 
 88 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
 89                                  struct autofs_wait_queue *wq,
 90                                  int type)
 91 {
 92         union {
 93                 struct autofs_packet_hdr hdr;
 94                 union autofs_packet_union v4_pkt;
 95                 union autofs_v5_packet_union v5_pkt;
 96         } pkt;
 97         struct file *pipe = NULL;
 98         size_t pktsz;
 99         int ret;
100 
101         pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
102                  (unsigned long) wq->wait_queue_token,
103                  wq->name.len, wq->name.name, type);
104 
105         memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
106 
107         pkt.hdr.proto_version = sbi->version;
108         pkt.hdr.type = type;
109 
110         switch (type) {
111         /* Kernel protocol v4 missing and expire packets */
112         case autofs_ptype_missing:
113         {
114                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
115 
116                 pktsz = sizeof(*mp);
117 
118                 mp->wait_queue_token = wq->wait_queue_token;
119                 mp->len = wq->name.len;
120                 memcpy(mp->name, wq->name.name, wq->name.len);
121                 mp->name[wq->name.len] = '\0';
122                 break;
123         }
124         case autofs_ptype_expire_multi:
125         {
126                 struct autofs_packet_expire_multi *ep =
127                                         &pkt.v4_pkt.expire_multi;
128 
129                 pktsz = sizeof(*ep);
130 
131                 ep->wait_queue_token = wq->wait_queue_token;
132                 ep->len = wq->name.len;
133                 memcpy(ep->name, wq->name.name, wq->name.len);
134                 ep->name[wq->name.len] = '\0';
135                 break;
136         }
137         /*
138          * Kernel protocol v5 packet for handling indirect and direct
139          * mount missing and expire requests
140          */
141         case autofs_ptype_missing_indirect:
142         case autofs_ptype_expire_indirect:
143         case autofs_ptype_missing_direct:
144         case autofs_ptype_expire_direct:
145         {
146                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
147                 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
148 
149                 pktsz = sizeof(*packet);
150 
151                 packet->wait_queue_token = wq->wait_queue_token;
152                 packet->len = wq->name.len;
153                 memcpy(packet->name, wq->name.name, wq->name.len);
154                 packet->name[wq->name.len] = '\0';
155                 packet->dev = wq->dev;
156                 packet->ino = wq->ino;
157                 packet->uid = from_kuid_munged(user_ns, wq->uid);
158                 packet->gid = from_kgid_munged(user_ns, wq->gid);
159                 packet->pid = wq->pid;
160                 packet->tgid = wq->tgid;
161                 break;
162         }
163         default:
164                 pr_warn("bad type %d!\n", type);
165                 mutex_unlock(&sbi->wq_mutex);
166                 return;
167         }
168 
169         pipe = get_file(sbi->pipe);
170 
171         mutex_unlock(&sbi->wq_mutex);
172 
173         switch (ret = autofs4_write(sbi, pipe, &pkt, pktsz)) {
174         case 0:
175                 break;
176         case -ENOMEM:
177         case -ERESTARTSYS:
178                 /* Just fail this one */
179                 autofs4_wait_release(sbi, wq->wait_queue_token, ret);
180                 break;
181         default:
182                 autofs4_catatonic_mode(sbi);
183                 break;
184         }
185         fput(pipe);
186 }
187 
188 static int autofs4_getpath(struct autofs_sb_info *sbi,
189                            struct dentry *dentry, char **name)
190 {
191         struct dentry *root = sbi->sb->s_root;
192         struct dentry *tmp;
193         char *buf;
194         char *p;
195         int len;
196         unsigned seq;
197 
198 rename_retry:
199         buf = *name;
200         len = 0;
201 
202         seq = read_seqbegin(&rename_lock);
203         rcu_read_lock();
204         spin_lock(&sbi->fs_lock);
205         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
206                 len += tmp->d_name.len + 1;
207 
208         if (!len || --len > NAME_MAX) {
209                 spin_unlock(&sbi->fs_lock);
210                 rcu_read_unlock();
211                 if (read_seqretry(&rename_lock, seq))
212                         goto rename_retry;
213                 return 0;
214         }
215 
216         *(buf + len) = '\0';
217         p = buf + len - dentry->d_name.len;
218         strncpy(p, dentry->d_name.name, dentry->d_name.len);
219 
220         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
221                 *(--p) = '/';
222                 p -= tmp->d_name.len;
223                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
224         }
225         spin_unlock(&sbi->fs_lock);
226         rcu_read_unlock();
227         if (read_seqretry(&rename_lock, seq))
228                 goto rename_retry;
229 
230         return len;
231 }
232 
233 static struct autofs_wait_queue *
234 autofs4_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
235 {
236         struct autofs_wait_queue *wq;
237 
238         for (wq = sbi->queues; wq; wq = wq->next) {
239                 if (wq->name.hash == qstr->hash &&
240                     wq->name.len == qstr->len &&
241                     wq->name.name &&
242                     !memcmp(wq->name.name, qstr->name, qstr->len))
243                         break;
244         }
245         return wq;
246 }
247 
248 /*
249  * Check if we have a valid request.
250  * Returns
251  * 1 if the request should continue.
252  *   In this case we can return an autofs_wait_queue entry if one is
253  *   found or NULL to idicate a new wait needs to be created.
254  * 0 or a negative errno if the request shouldn't continue.
255  */
256 static int validate_request(struct autofs_wait_queue **wait,
257                             struct autofs_sb_info *sbi,
258                             const struct qstr *qstr,
259                             const struct path *path, enum autofs_notify notify)
260 {
261         struct dentry *dentry = path->dentry;
262         struct autofs_wait_queue *wq;
263         struct autofs_info *ino;
264 
265         if (sbi->catatonic)
266                 return -ENOENT;
267 
268         /* Wait in progress, continue; */
269         wq = autofs4_find_wait(sbi, qstr);
270         if (wq) {
271                 *wait = wq;
272                 return 1;
273         }
274 
275         *wait = NULL;
276 
277         /* If we don't yet have any info this is a new request */
278         ino = autofs4_dentry_ino(dentry);
279         if (!ino)
280                 return 1;
281 
282         /*
283          * If we've been asked to wait on an existing expire (NFY_NONE)
284          * but there is no wait in the queue ...
285          */
286         if (notify == NFY_NONE) {
287                 /*
288                  * Either we've betean the pending expire to post it's
289                  * wait or it finished while we waited on the mutex.
290                  * So we need to wait till either, the wait appears
291                  * or the expire finishes.
292                  */
293 
294                 while (ino->flags & AUTOFS_INF_EXPIRING) {
295                         mutex_unlock(&sbi->wq_mutex);
296                         schedule_timeout_interruptible(HZ/10);
297                         if (mutex_lock_interruptible(&sbi->wq_mutex))
298                                 return -EINTR;
299 
300                         if (sbi->catatonic)
301                                 return -ENOENT;
302 
303                         wq = autofs4_find_wait(sbi, qstr);
304                         if (wq) {
305                                 *wait = wq;
306                                 return 1;
307                         }
308                 }
309 
310                 /*
311                  * Not ideal but the status has already gone. Of the two
312                  * cases where we wait on NFY_NONE neither depend on the
313                  * return status of the wait.
314                  */
315                 return 0;
316         }
317 
318         /*
319          * If we've been asked to trigger a mount and the request
320          * completed while we waited on the mutex ...
321          */
322         if (notify == NFY_MOUNT) {
323                 struct dentry *new = NULL;
324                 struct path this;
325                 int valid = 1;
326 
327                 /*
328                  * If the dentry was successfully mounted while we slept
329                  * on the wait queue mutex we can return success. If it
330                  * isn't mounted (doesn't have submounts for the case of
331                  * a multi-mount with no mount at it's base) we can
332                  * continue on and create a new request.
333                  */
334                 if (!IS_ROOT(dentry)) {
335                         if (d_unhashed(dentry) &&
336                             d_really_is_positive(dentry)) {
337                                 struct dentry *parent = dentry->d_parent;
338 
339                                 new = d_lookup(parent, &dentry->d_name);
340                                 if (new)
341                                         dentry = new;
342                         }
343                 }
344                 this.mnt = path->mnt;
345                 this.dentry = dentry;
346                 if (path_has_submounts(&this))
347                         valid = 0;
348 
349                 if (new)
350                         dput(new);
351                 return valid;
352         }
353 
354         return 1;
355 }
356 
357 int autofs4_wait(struct autofs_sb_info *sbi,
358                  const struct path *path, enum autofs_notify notify)
359 {
360         struct dentry *dentry = path->dentry;
361         struct autofs_wait_queue *wq;
362         struct qstr qstr;
363         char *name;
364         int status, ret, type;
365         pid_t pid;
366         pid_t tgid;
367 
368         /* In catatonic mode, we don't wait for nobody */
369         if (sbi->catatonic)
370                 return -ENOENT;
371 
372         /*
373          * Try translating pids to the namespace of the daemon.
374          *
375          * Zero means failure: we are in an unrelated pid namespace.
376          */
377         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
378         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
379         if (pid == 0 || tgid == 0)
380                 return -ENOENT;
381 
382         if (d_really_is_negative(dentry)) {
383                 /*
384                  * A wait for a negative dentry is invalid for certain
385                  * cases. A direct or offset mount "always" has its mount
386                  * point directory created and so the request dentry must
387                  * be positive or the map key doesn't exist. The situation
388                  * is very similar for indirect mounts except only dentrys
389                  * in the root of the autofs file system may be negative.
390                  */
391                 if (autofs_type_trigger(sbi->type))
392                         return -ENOENT;
393                 else if (!IS_ROOT(dentry->d_parent))
394                         return -ENOENT;
395         }
396 
397         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
398         if (!name)
399                 return -ENOMEM;
400 
401         /* If this is a direct mount request create a dummy name */
402         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
403                 qstr.len = sprintf(name, "%p", dentry);
404         else {
405                 qstr.len = autofs4_getpath(sbi, dentry, &name);
406                 if (!qstr.len) {
407                         kfree(name);
408                         return -ENOENT;
409                 }
410         }
411         qstr.name = name;
412         qstr.hash = full_name_hash(dentry, name, qstr.len);
413 
414         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
415                 kfree(qstr.name);
416                 return -EINTR;
417         }
418 
419         ret = validate_request(&wq, sbi, &qstr, path, notify);
420         if (ret <= 0) {
421                 if (ret != -EINTR)
422                         mutex_unlock(&sbi->wq_mutex);
423                 kfree(qstr.name);
424                 return ret;
425         }
426 
427         if (!wq) {
428                 /* Create a new wait queue */
429                 wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
430                 if (!wq) {
431                         kfree(qstr.name);
432                         mutex_unlock(&sbi->wq_mutex);
433                         return -ENOMEM;
434                 }
435 
436                 wq->wait_queue_token = autofs4_next_wait_queue;
437                 if (++autofs4_next_wait_queue == 0)
438                         autofs4_next_wait_queue = 1;
439                 wq->next = sbi->queues;
440                 sbi->queues = wq;
441                 init_waitqueue_head(&wq->queue);
442                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
443                 wq->dev = autofs4_get_dev(sbi);
444                 wq->ino = autofs4_get_ino(sbi);
445                 wq->uid = current_uid();
446                 wq->gid = current_gid();
447                 wq->pid = pid;
448                 wq->tgid = tgid;
449                 wq->status = -EINTR; /* Status return if interrupted */
450                 wq->wait_ctr = 2;
451 
452                 if (sbi->version < 5) {
453                         if (notify == NFY_MOUNT)
454                                 type = autofs_ptype_missing;
455                         else
456                                 type = autofs_ptype_expire_multi;
457                 } else {
458                         if (notify == NFY_MOUNT)
459                                 type = autofs_type_trigger(sbi->type) ?
460                                         autofs_ptype_missing_direct :
461                                          autofs_ptype_missing_indirect;
462                         else
463                                 type = autofs_type_trigger(sbi->type) ?
464                                         autofs_ptype_expire_direct :
465                                         autofs_ptype_expire_indirect;
466                 }
467 
468                 pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
469                          (unsigned long) wq->wait_queue_token, wq->name.len,
470                          wq->name.name, notify);
471 
472                 /*
473                  * autofs4_notify_daemon() may block; it will unlock ->wq_mutex
474                  */
475                 autofs4_notify_daemon(sbi, wq, type);
476         } else {
477                 wq->wait_ctr++;
478                 pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
479                          (unsigned long) wq->wait_queue_token, wq->name.len,
480                          wq->name.name, notify);
481                 mutex_unlock(&sbi->wq_mutex);
482                 kfree(qstr.name);
483         }
484 
485         /*
486          * wq->name.name is NULL iff the lock is already released
487          * or the mount has been made catatonic.
488          */
489         if (wq->name.name) {
490                 /* Block all but "shutdown" signals while waiting */
491                 unsigned long shutdown_sigs_mask;
492                 unsigned long irqflags;
493                 sigset_t oldset;
494 
495                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
496                 oldset = current->blocked;
497                 shutdown_sigs_mask = SHUTDOWN_SIGS & ~oldset.sig[0];
498                 siginitsetinv(&current->blocked, shutdown_sigs_mask);
499                 recalc_sigpending();
500                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
501 
502                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
503 
504                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
505                 current->blocked = oldset;
506                 recalc_sigpending();
507                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
508         } else {
509                 pr_debug("skipped sleeping\n");
510         }
511 
512         status = wq->status;
513 
514         /*
515          * For direct and offset mounts we need to track the requester's
516          * uid and gid in the dentry info struct. This is so it can be
517          * supplied, on request, by the misc device ioctl interface.
518          * This is needed during daemon resatart when reconnecting
519          * to existing, active, autofs mounts. The uid and gid (and
520          * related string values) may be used for macro substitution
521          * in autofs mount maps.
522          */
523         if (!status) {
524                 struct autofs_info *ino;
525                 struct dentry *de = NULL;
526 
527                 /* direct mount or browsable map */
528                 ino = autofs4_dentry_ino(dentry);
529                 if (!ino) {
530                         /* If not lookup actual dentry used */
531                         de = d_lookup(dentry->d_parent, &dentry->d_name);
532                         if (de)
533                                 ino = autofs4_dentry_ino(de);
534                 }
535 
536                 /* Set mount requester */
537                 if (ino) {
538                         spin_lock(&sbi->fs_lock);
539                         ino->uid = wq->uid;
540                         ino->gid = wq->gid;
541                         spin_unlock(&sbi->fs_lock);
542                 }
543 
544                 if (de)
545                         dput(de);
546         }
547 
548         /* Are we the last process to need status? */
549         mutex_lock(&sbi->wq_mutex);
550         if (!--wq->wait_ctr)
551                 kfree(wq);
552         mutex_unlock(&sbi->wq_mutex);
553 
554         return status;
555 }
556 
557 
558 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
559 {
560         struct autofs_wait_queue *wq, **wql;
561 
562         mutex_lock(&sbi->wq_mutex);
563         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
564                 if (wq->wait_queue_token == wait_queue_token)
565                         break;
566         }
567 
568         if (!wq) {
569                 mutex_unlock(&sbi->wq_mutex);
570                 return -EINVAL;
571         }
572 
573         *wql = wq->next;        /* Unlink from chain */
574         kfree(wq->name.name);
575         wq->name.name = NULL;   /* Do not wait on this queue */
576         wq->status = status;
577         wake_up_interruptible(&wq->queue);
578         if (!--wq->wait_ctr)
579                 kfree(wq);
580         mutex_unlock(&sbi->wq_mutex);
581 
582         return 0;
583 }
584 

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