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/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_cred()->uid;
 446                 wq->gid = current_cred()->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 }