fs/autofs/waitq.c

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