fs/autofs4/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/slab.h>
  11 #include <linux/time.h>
  12 #include <linux/signal.h>
  13 #include <linux/file.h>
  14 #include "autofs_i.h"
  15
  16 /* We make this a static variable rather than a part of the superblock; it
  17  * is better if we don't reassign numbers easily even across filesystems
  18  */
  19 static autofs_wqt_t autofs4_next_wait_queue = 1;
  20
  21 /* These are the signals we allow interrupting a pending mount */
  22 #define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
  23
  24 void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
  25 {
  26         struct autofs_wait_queue *wq, *nwq;
  27
  28         mutex_lock(&sbi->wq_mutex);
  29         if (sbi->catatonic) {
  30                 mutex_unlock(&sbi->wq_mutex);
  31                 return;
  32         }
  33
  34         pr_debug("entering catatonic mode\n");
  35
  36         sbi->catatonic = 1;
  37         wq = sbi->queues;
  38         sbi->queues = NULL;     /* Erase all wait queues */
  39         while (wq) {
  40                 nwq = wq->next;
  41                 wq->status = -ENOENT; /* Magic is gone - report failure */
  42                 kfree(wq->name.name);
  43                 wq->name.name = NULL;
  44                 wq->wait_ctr--;
  45                 wake_up_interruptible(&wq->queue);
  46                 wq = nwq;
  47         }
  48         fput(sbi->pipe);        /* Close the pipe */
  49         sbi->pipe = NULL;
  50         sbi->pipefd = -1;
  51         mutex_unlock(&sbi->wq_mutex);
  52 }
  53
  54 static int autofs4_write(struct autofs_sb_info *sbi,
  55                          struct file *file, const void *addr, int bytes)
  56 {
  57         unsigned long sigpipe, flags;
  58         mm_segment_t fs;
  59         const char *data = (const char *)addr;
  60         ssize_t wr = 0;
  61
  62         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  63
  64         /* Save pointer to user space and point back to kernel space */
  65         fs = get_fs();
  66         set_fs(KERNEL_DS);
  67
  68         mutex_lock(&sbi->pipe_mutex);
  69         while (bytes) {
  70                 wr = __vfs_write(file, data, bytes, &file->f_pos);
  71                 if (wr <= 0)
  72                         break;
  73                 data += wr;
  74                 bytes -= wr;
  75         }
  76         mutex_unlock(&sbi->pipe_mutex);
  77
  78         set_fs(fs);
  79
  80         /* Keep the currently executing process from receiving a
  81          * SIGPIPE unless it was already supposed to get one
  82          */
  83         if (wr == -EPIPE && !sigpipe) {
  84                 spin_lock_irqsave(&current->sighand->siglock, flags);
  85                 sigdelset(&current->pending.signal, SIGPIPE);
  86                 recalc_sigpending();
  87                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  88         }
  89
  90         return (bytes > 0);
  91 }
  92
  93 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  94                                  struct autofs_wait_queue *wq,
  95                                  int type)
  96 {
  97         union {
  98                 struct autofs_packet_hdr hdr;
  99                 union autofs_packet_union v4_pkt;
 100                 union autofs_v5_packet_union v5_pkt;
 101         } pkt;
 102         struct file *pipe = NULL;
 103         size_t pktsz;
 104
 105         pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
 106                  (unsigned long) wq->wait_queue_token,
 107                  wq->name.len, wq->name.name, type);
 108
 109         memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
 110
 111         pkt.hdr.proto_version = sbi->version;
 112         pkt.hdr.type = type;
 113
 114         switch (type) {
 115         /* Kernel protocol v4 missing and expire packets */
 116         case autofs_ptype_missing:
 117         {
 118                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 119
 120                 pktsz = sizeof(*mp);
 121
 122                 mp->wait_queue_token = wq->wait_queue_token;
 123                 mp->len = wq->name.len;
 124                 memcpy(mp->name, wq->name.name, wq->name.len);
 125                 mp->name[wq->name.len] = '\0';
 126                 break;
 127         }
 128         case autofs_ptype_expire_multi:
 129         {
 130                 struct autofs_packet_expire_multi *ep =
 131                                         &pkt.v4_pkt.expire_multi;
 132
 133                 pktsz = sizeof(*ep);
 134
 135                 ep->wait_queue_token = wq->wait_queue_token;
 136                 ep->len = wq->name.len;
 137                 memcpy(ep->name, wq->name.name, wq->name.len);
 138                 ep->name[wq->name.len] = '\0';
 139                 break;
 140         }
 141         /*
 142          * Kernel protocol v5 packet for handling indirect and direct
 143          * mount missing and expire requests
 144          */
 145         case autofs_ptype_missing_indirect:
 146         case autofs_ptype_expire_indirect:
 147         case autofs_ptype_missing_direct:
 148         case autofs_ptype_expire_direct:
 149         {
 150                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 151                 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
 152
 153                 pktsz = sizeof(*packet);
 154
 155                 packet->wait_queue_token = wq->wait_queue_token;
 156                 packet->len = wq->name.len;
 157                 memcpy(packet->name, wq->name.name, wq->name.len);
 158                 packet->name[wq->name.len] = '\0';
 159                 packet->dev = wq->dev;
 160                 packet->ino = wq->ino;
 161                 packet->uid = from_kuid_munged(user_ns, wq->uid);
 162                 packet->gid = from_kgid_munged(user_ns, wq->gid);
 163                 packet->pid = wq->pid;
 164                 packet->tgid = wq->tgid;
 165                 break;
 166         }
 167         default:
 168                 pr_warn("bad type %d!\n", type);
 169                 mutex_unlock(&sbi->wq_mutex);
 170                 return;
 171         }
 172
 173         pipe = get_file(sbi->pipe);
 174
 175         mutex_unlock(&sbi->wq_mutex);
 176
 177         if (autofs4_write(sbi, pipe, &pkt, pktsz))
 178                 autofs4_catatonic_mode(sbi);
 179         fput(pipe);
 180 }
 181
 182 static int autofs4_getpath(struct autofs_sb_info *sbi,
 183                            struct dentry *dentry, char **name)
 184 {
 185         struct dentry *root = sbi->sb->s_root;
 186         struct dentry *tmp;
 187         char *buf;
 188         char *p;
 189         int len;
 190         unsigned seq;
 191
 192 rename_retry:
 193         buf = *name;
 194         len = 0;
 195
 196         seq = read_seqbegin(&rename_lock);
 197         rcu_read_lock();
 198         spin_lock(&sbi->fs_lock);
 199         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 200                 len += tmp->d_name.len + 1;
 201
 202         if (!len || --len > NAME_MAX) {
 203                 spin_unlock(&sbi->fs_lock);
 204                 rcu_read_unlock();
 205                 if (read_seqretry(&rename_lock, seq))
 206                         goto rename_retry;
 207                 return 0;
 208         }
 209
 210         *(buf + len) = '\0';
 211         p = buf + len - dentry->d_name.len;
 212         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 213
 214         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 215                 *(--p) = '/';
 216                 p -= tmp->d_name.len;
 217                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 218         }
 219         spin_unlock(&sbi->fs_lock);
 220         rcu_read_unlock();
 221         if (read_seqretry(&rename_lock, seq))
 222                 goto rename_retry;
 223
 224         return len;
 225 }
 226
 227 static struct autofs_wait_queue *
 228 autofs4_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
 229 {
 230         struct autofs_wait_queue *wq;
 231
 232         for (wq = sbi->queues; wq; wq = wq->next) {
 233                 if (wq->name.hash == qstr->hash &&
 234                     wq->name.len == qstr->len &&
 235                     wq->name.name &&
 236                     !memcmp(wq->name.name, qstr->name, qstr->len))
 237                         break;
 238         }
 239         return wq;
 240 }
 241
 242 /*
 243  * Check if we have a valid request.
 244  * Returns
 245  * 1 if the request should continue.
 246  *   In this case we can return an autofs_wait_queue entry if one is
 247  *   found or NULL to idicate a new wait needs to be created.
 248  * 0 or a negative errno if the request shouldn't continue.
 249  */
 250 static int validate_request(struct autofs_wait_queue **wait,
 251                             struct autofs_sb_info *sbi,
 252                             const struct qstr *qstr,
 253                             const struct path *path, enum autofs_notify notify)
 254 {
 255         struct dentry *dentry = path->dentry;
 256         struct autofs_wait_queue *wq;
 257         struct autofs_info *ino;
 258
 259         if (sbi->catatonic)
 260                 return -ENOENT;
 261
 262         /* Wait in progress, continue; */
 263         wq = autofs4_find_wait(sbi, qstr);
 264         if (wq) {
 265                 *wait = wq;
 266                 return 1;
 267         }
 268
 269         *wait = NULL;
 270
 271         /* If we don't yet have any info this is a new request */
 272         ino = autofs4_dentry_ino(dentry);
 273         if (!ino)
 274                 return 1;
 275
 276         /*
 277          * If we've been asked to wait on an existing expire (NFY_NONE)
 278          * but there is no wait in the queue ...
 279          */
 280         if (notify == NFY_NONE) {
 281                 /*
 282                  * Either we've betean the pending expire to post it's
 283                  * wait or it finished while we waited on the mutex.
 284                  * So we need to wait till either, the wait appears
 285                  * or the expire finishes.
 286                  */
 287
 288                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 289                         mutex_unlock(&sbi->wq_mutex);
 290                         schedule_timeout_interruptible(HZ/10);
 291                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 292                                 return -EINTR;
 293
 294                         if (sbi->catatonic)
 295                                 return -ENOENT;
 296
 297                         wq = autofs4_find_wait(sbi, qstr);
 298                         if (wq) {
 299                                 *wait = wq;
 300                                 return 1;
 301                         }
 302                 }
 303
 304                 /*
 305                  * Not ideal but the status has already gone. Of the two
 306                  * cases where we wait on NFY_NONE neither depend on the
 307                  * return status of the wait.
 308                  */
 309                 return 0;
 310         }
 311
 312         /*
 313          * If we've been asked to trigger a mount and the request
 314          * completed while we waited on the mutex ...
 315          */
 316         if (notify == NFY_MOUNT) {
 317                 struct dentry *new = NULL;
 318                 struct path this;
 319                 int valid = 1;
 320
 321                 /*
 322                  * If the dentry was successfully mounted while we slept
 323                  * on the wait queue mutex we can return success. If it
 324                  * isn't mounted (doesn't have submounts for the case of
 325                  * a multi-mount with no mount at it's base) we can
 326                  * continue on and create a new request.
 327                  */
 328                 if (!IS_ROOT(dentry)) {
 329                         if (d_unhashed(dentry) &&
 330                             d_really_is_positive(dentry)) {
 331                                 struct dentry *parent = dentry->d_parent;
 332
 333                                 new = d_lookup(parent, &dentry->d_name);
 334                                 if (new)
 335                                         dentry = new;
 336                         }
 337                 }
 338                 this.mnt = path->mnt;
 339                 this.dentry = dentry;
 340                 if (path_has_submounts(&this))
 341                         valid = 0;
 342
 343                 if (new)
 344                         dput(new);
 345                 return valid;
 346         }
 347
 348         return 1;
 349 }
 350
 351 int autofs4_wait(struct autofs_sb_info *sbi,
 352                  const struct path *path, enum autofs_notify notify)
 353 {
 354         struct dentry *dentry = path->dentry;
 355         struct autofs_wait_queue *wq;
 356         struct qstr qstr;
 357         char *name;
 358         int status, ret, type;
 359         pid_t pid;
 360         pid_t tgid;
 361
 362         /* In catatonic mode, we don't wait for nobody */
 363         if (sbi->catatonic)
 364                 return -ENOENT;
 365
 366         /*
 367          * Try translating pids to the namespace of the daemon.
 368          *
 369          * Zero means failure: we are in an unrelated pid namespace.
 370          */
 371         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 372         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 373         if (pid == 0 || tgid == 0)
 374                 return -ENOENT;
 375
 376         if (d_really_is_negative(dentry)) {
 377                 /*
 378                  * A wait for a negative dentry is invalid for certain
 379                  * cases. A direct or offset mount "always" has its mount
 380                  * point directory created and so the request dentry must
 381                  * be positive or the map key doesn't exist. The situation
 382                  * is very similar for indirect mounts except only dentrys
 383                  * in the root of the autofs file system may be negative.
 384                  */
 385                 if (autofs_type_trigger(sbi->type))
 386                         return -ENOENT;
 387                 else if (!IS_ROOT(dentry->d_parent))
 388                         return -ENOENT;
 389         }
 390
 391         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 392         if (!name)
 393                 return -ENOMEM;
 394
 395         /* If this is a direct mount request create a dummy name */
 396         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 397                 qstr.len = sprintf(name, "%p", dentry);
 398         else {
 399                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 400                 if (!qstr.len) {
 401                         kfree(name);
 402                         return -ENOENT;
 403                 }
 404         }
 405         qstr.name = name;
 406         qstr.hash = full_name_hash(dentry, name, qstr.len);
 407
 408         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 409                 kfree(qstr.name);
 410                 return -EINTR;
 411         }
 412
 413         ret = validate_request(&wq, sbi, &qstr, path, notify);
 414         if (ret <= 0) {
 415                 if (ret != -EINTR)
 416                         mutex_unlock(&sbi->wq_mutex);
 417                 kfree(qstr.name);
 418                 return ret;
 419         }
 420
 421         if (!wq) {
 422                 /* Create a new wait queue */
 423                 wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
 424                 if (!wq) {
 425                         kfree(qstr.name);
 426                         mutex_unlock(&sbi->wq_mutex);
 427                         return -ENOMEM;
 428                 }
 429
 430                 wq->wait_queue_token = autofs4_next_wait_queue;
 431                 if (++autofs4_next_wait_queue == 0)
 432                         autofs4_next_wait_queue = 1;
 433                 wq->next = sbi->queues;
 434                 sbi->queues = wq;
 435                 init_waitqueue_head(&wq->queue);
 436                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 437                 wq->dev = autofs4_get_dev(sbi);
 438                 wq->ino = autofs4_get_ino(sbi);
 439                 wq->uid = current_real_cred()->uid;
 440                 wq->gid = current_real_cred()->gid;
 441                 wq->pid = pid;
 442                 wq->tgid = tgid;
 443                 wq->status = -EINTR; /* Status return if interrupted */
 444                 wq->wait_ctr = 2;
 445
 446                 if (sbi->version < 5) {
 447                         if (notify == NFY_MOUNT)
 448                                 type = autofs_ptype_missing;
 449                         else
 450                                 type = autofs_ptype_expire_multi;
 451                 } else {
 452                         if (notify == NFY_MOUNT)
 453                                 type = autofs_type_trigger(sbi->type) ?
 454                                         autofs_ptype_missing_direct :
 455                                          autofs_ptype_missing_indirect;
 456                         else
 457                                 type = autofs_type_trigger(sbi->type) ?
 458                                         autofs_ptype_expire_direct :
 459                                         autofs_ptype_expire_indirect;
 460                 }
 461
 462                 pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 463                          (unsigned long) wq->wait_queue_token, wq->name.len,
 464                          wq->name.name, notify);
 465
 466                 /*
 467                  * autofs4_notify_daemon() may block; it will unlock ->wq_mutex
 468                  */
 469                 autofs4_notify_daemon(sbi, wq, type);
 470         } else {
 471                 wq->wait_ctr++;
 472                 pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 473                          (unsigned long) wq->wait_queue_token, wq->name.len,
 474                          wq->name.name, notify);
 475                 mutex_unlock(&sbi->wq_mutex);
 476                 kfree(qstr.name);
 477         }
 478
 479         /*
 480          * wq->name.name is NULL iff the lock is already released
 481          * or the mount has been made catatonic.
 482          */
 483         if (wq->name.name) {
 484                 /* Block all but "shutdown" signals while waiting */
 485                 unsigned long shutdown_sigs_mask;
 486                 unsigned long irqflags;
 487                 sigset_t oldset;
 488
 489                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 490                 oldset = current->blocked;
 491                 shutdown_sigs_mask = SHUTDOWN_SIGS & ~oldset.sig[0];
 492                 siginitsetinv(&current->blocked, shutdown_sigs_mask);
 493                 recalc_sigpending();
 494                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 495
 496                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 497
 498                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 499                 current->blocked = oldset;
 500                 recalc_sigpending();
 501                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 502         } else {
 503                 pr_debug("skipped sleeping\n");
 504         }
 505
 506         status = wq->status;
 507
 508         /*
 509          * For direct and offset mounts we need to track the requester's
 510          * uid and gid in the dentry info struct. This is so it can be
 511          * supplied, on request, by the misc device ioctl interface.
 512          * This is needed during daemon resatart when reconnecting
 513          * to existing, active, autofs mounts. The uid and gid (and
 514          * related string values) may be used for macro substitution
 515          * in autofs mount maps.
 516          */
 517         if (!status) {
 518                 struct autofs_info *ino;
 519                 struct dentry *de = NULL;
 520
 521                 /* direct mount or browsable map */
 522                 ino = autofs4_dentry_ino(dentry);
 523                 if (!ino) {
 524                         /* If not lookup actual dentry used */
 525                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 526                         if (de)
 527                                 ino = autofs4_dentry_ino(de);
 528                 }
 529
 530                 /* Set mount requester */
 531                 if (ino) {
 532                         spin_lock(&sbi->fs_lock);
 533                         ino->uid = wq->uid;
 534                         ino->gid = wq->gid;
 535                         spin_unlock(&sbi->fs_lock);
 536                 }
 537
 538                 if (de)
 539                         dput(de);
 540         }
 541
 542         /* Are we the last process to need status? */
 543         mutex_lock(&sbi->wq_mutex);
 544         if (!--wq->wait_ctr)
 545                 kfree(wq);
 546         mutex_unlock(&sbi->wq_mutex);
 547
 548         return status;
 549 }
 550
 551
 552 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 553 {
 554         struct autofs_wait_queue *wq, **wql;
 555
 556         mutex_lock(&sbi->wq_mutex);
 557         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 558                 if (wq->wait_queue_token == wait_queue_token)
 559                         break;
 560         }
 561
 562         if (!wq) {
 563                 mutex_unlock(&sbi->wq_mutex);
 564                 return -EINVAL;
 565         }
 566
 567         *wql = wq->next;        /* Unlink from chain */
 568         kfree(wq->name.name);
 569         wq->name.name = NULL;   /* Do not wait on this queue */
 570         wq->status = status;
 571         wake_up_interruptible(&wq->queue);
 572         if (!--wq->wait_ctr)
 573                 kfree(wq);
 574         mutex_unlock(&sbi->wq_mutex);
 575
 576         return 0;
 577 }