fs/autofs/waitq.c

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