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         wr = __vfs_write(file, data, bytes, &file->f_pos);
  70         while (bytes && wr) {
  71                 data += wr;
  72                 bytes -= wr;
  73                 wr = __vfs_write(file, data, bytes, &file->f_pos);
  74         }
  75         mutex_unlock(&sbi->pipe_mutex);
  76
  77         set_fs(fs);
  78
  79         /* Keep the currently executing process from receiving a
  80          * SIGPIPE unless it was already supposed to get one
  81          */
  82         if (wr == -EPIPE && !sigpipe) {
  83                 spin_lock_irqsave(&current->sighand->siglock, flags);
  84                 sigdelset(&current->pending.signal, SIGPIPE);
  85                 recalc_sigpending();
  86                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  87         }
  88
  89         return (bytes > 0);
  90 }
  91
  92 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  93                                  struct autofs_wait_queue *wq,
  94                                  int type)
  95 {
  96         union {
  97                 struct autofs_packet_hdr hdr;
  98                 union autofs_packet_union v4_pkt;
  99                 union autofs_v5_packet_union v5_pkt;
 100         } pkt;
 101         struct file *pipe = NULL;
 102         size_t pktsz;
 103
 104         pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
 105                  (unsigned long) wq->wait_queue_token,
 106                  wq->name.len, wq->name.name, type);
 107
 108         memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
 109
 110         pkt.hdr.proto_version = sbi->version;
 111         pkt.hdr.type = type;
 112
 113         switch (type) {
 114         /* Kernel protocol v4 missing and expire packets */
 115         case autofs_ptype_missing:
 116         {
 117                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 118
 119                 pktsz = sizeof(*mp);
 120
 121                 mp->wait_queue_token = wq->wait_queue_token;
 122                 mp->len = wq->name.len;
 123                 memcpy(mp->name, wq->name.name, wq->name.len);
 124                 mp->name[wq->name.len] = '\0';
 125                 break;
 126         }
 127         case autofs_ptype_expire_multi:
 128         {
 129                 struct autofs_packet_expire_multi *ep =
 130                                         &pkt.v4_pkt.expire_multi;
 131
 132                 pktsz = sizeof(*ep);
 133
 134                 ep->wait_queue_token = wq->wait_queue_token;
 135                 ep->len = wq->name.len;
 136                 memcpy(ep->name, wq->name.name, wq->name.len);
 137                 ep->name[wq->name.len] = '\0';
 138                 break;
 139         }
 140         /*
 141          * Kernel protocol v5 packet for handling indirect and direct
 142          * mount missing and expire requests
 143          */
 144         case autofs_ptype_missing_indirect:
 145         case autofs_ptype_expire_indirect:
 146         case autofs_ptype_missing_direct:
 147         case autofs_ptype_expire_direct:
 148         {
 149                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 150                 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
 151
 152                 pktsz = sizeof(*packet);
 153
 154                 packet->wait_queue_token = wq->wait_queue_token;
 155                 packet->len = wq->name.len;
 156                 memcpy(packet->name, wq->name.name, wq->name.len);
 157                 packet->name[wq->name.len] = '\0';
 158                 packet->dev = wq->dev;
 159                 packet->ino = wq->ino;
 160                 packet->uid = from_kuid_munged(user_ns, wq->uid);
 161                 packet->gid = from_kgid_munged(user_ns, wq->gid);
 162                 packet->pid = wq->pid;
 163                 packet->tgid = wq->tgid;
 164                 break;
 165         }
 166         default:
 167                 pr_warn("bad type %d!\n", type);
 168                 mutex_unlock(&sbi->wq_mutex);
 169                 return;
 170         }
 171
 172         pipe = get_file(sbi->pipe);
 173
 174         mutex_unlock(&sbi->wq_mutex);
 175
 176         if (autofs4_write(sbi, pipe, &pkt, pktsz))
 177                 autofs4_catatonic_mode(sbi);
 178         fput(pipe);
 179 }
 180
 181 static int autofs4_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 autofs4_find_wait(struct autofs_sb_info *sbi, 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                             struct qstr *qstr,
 252                             struct dentry *dentry, enum autofs_notify notify)
 253 {
 254         struct autofs_wait_queue *wq;
 255         struct autofs_info *ino;
 256
 257         if (sbi->catatonic)
 258                 return -ENOENT;
 259
 260         /* Wait in progress, continue; */
 261         wq = autofs4_find_wait(sbi, qstr);
 262         if (wq) {
 263                 *wait = wq;
 264                 return 1;
 265         }
 266
 267         *wait = NULL;
 268
 269         /* If we don't yet have any info this is a new request */
 270         ino = autofs4_dentry_ino(dentry);
 271         if (!ino)
 272                 return 1;
 273
 274         /*
 275          * If we've been asked to wait on an existing expire (NFY_NONE)
 276          * but there is no wait in the queue ...
 277          */
 278         if (notify == NFY_NONE) {
 279                 /*
 280                  * Either we've betean the pending expire to post it's
 281                  * wait or it finished while we waited on the mutex.
 282                  * So we need to wait till either, the wait appears
 283                  * or the expire finishes.
 284                  */
 285
 286                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 287                         mutex_unlock(&sbi->wq_mutex);
 288                         schedule_timeout_interruptible(HZ/10);
 289                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 290                                 return -EINTR;
 291
 292                         if (sbi->catatonic)
 293                                 return -ENOENT;
 294
 295                         wq = autofs4_find_wait(sbi, qstr);
 296                         if (wq) {
 297                                 *wait = wq;
 298                                 return 1;
 299                         }
 300                 }
 301
 302                 /*
 303                  * Not ideal but the status has already gone. Of the two
 304                  * cases where we wait on NFY_NONE neither depend on the
 305                  * return status of the wait.
 306                  */
 307                 return 0;
 308         }
 309
 310         /*
 311          * If we've been asked to trigger a mount and the request
 312          * completed while we waited on the mutex ...
 313          */
 314         if (notify == NFY_MOUNT) {
 315                 struct dentry *new = NULL;
 316                 int valid = 1;
 317
 318                 /*
 319                  * If the dentry was successfully mounted while we slept
 320                  * on the wait queue mutex we can return success. If it
 321                  * isn't mounted (doesn't have submounts for the case of
 322                  * a multi-mount with no mount at it's base) we can
 323                  * continue on and create a new request.
 324                  */
 325                 if (!IS_ROOT(dentry)) {
 326                         if (d_unhashed(dentry) &&
 327                             d_really_is_positive(dentry)) {
 328                                 struct dentry *parent = dentry->d_parent;
 329
 330                                 new = d_lookup(parent, &dentry->d_name);
 331                                 if (new)
 332                                         dentry = new;
 333                         }
 334                 }
 335                 if (have_submounts(dentry))
 336                         valid = 0;
 337
 338                 if (new)
 339                         dput(new);
 340                 return valid;
 341         }
 342
 343         return 1;
 344 }
 345
 346 int autofs4_wait(struct autofs_sb_info *sbi,
 347                  struct dentry *dentry, enum autofs_notify notify)
 348 {
 349         struct autofs_wait_queue *wq;
 350         struct qstr qstr;
 351         char *name;
 352         int status, ret, type;
 353         pid_t pid;
 354         pid_t tgid;
 355
 356         /* In catatonic mode, we don't wait for nobody */
 357         if (sbi->catatonic)
 358                 return -ENOENT;
 359
 360         /*
 361          * Try translating pids to the namespace of the daemon.
 362          *
 363          * Zero means failure: we are in an unrelated pid namespace.
 364          */
 365         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 366         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 367         if (pid == 0 || tgid == 0)
 368                 return -ENOENT;
 369
 370         if (d_really_is_negative(dentry)) {
 371                 /*
 372                  * A wait for a negative dentry is invalid for certain
 373                  * cases. A direct or offset mount "always" has its mount
 374                  * point directory created and so the request dentry must
 375                  * be positive or the map key doesn't exist. The situation
 376                  * is very similar for indirect mounts except only dentrys
 377                  * in the root of the autofs file system may be negative.
 378                  */
 379                 if (autofs_type_trigger(sbi->type))
 380                         return -ENOENT;
 381                 else if (!IS_ROOT(dentry->d_parent))
 382                         return -ENOENT;
 383         }
 384
 385         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 386         if (!name)
 387                 return -ENOMEM;
 388
 389         /* If this is a direct mount request create a dummy name */
 390         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 391                 qstr.len = sprintf(name, "%p", dentry);
 392         else {
 393                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 394                 if (!qstr.len) {
 395                         kfree(name);
 396                         return -ENOENT;
 397                 }
 398         }
 399         qstr.name = name;
 400         qstr.hash = full_name_hash(name, qstr.len);
 401
 402         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 403                 kfree(qstr.name);
 404                 return -EINTR;
 405         }
 406
 407         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 408         if (ret <= 0) {
 409                 if (ret != -EINTR)
 410                         mutex_unlock(&sbi->wq_mutex);
 411                 kfree(qstr.name);
 412                 return ret;
 413         }
 414
 415         if (!wq) {
 416                 /* Create a new wait queue */
 417                 wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
 418                 if (!wq) {
 419                         kfree(qstr.name);
 420                         mutex_unlock(&sbi->wq_mutex);
 421                         return -ENOMEM;
 422                 }
 423
 424                 wq->wait_queue_token = autofs4_next_wait_queue;
 425                 if (++autofs4_next_wait_queue == 0)
 426                         autofs4_next_wait_queue = 1;
 427                 wq->next = sbi->queues;
 428                 sbi->queues = wq;
 429                 init_waitqueue_head(&wq->queue);
 430                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 431                 wq->dev = autofs4_get_dev(sbi);
 432                 wq->ino = autofs4_get_ino(sbi);
 433                 wq->uid = current_uid();
 434                 wq->gid = current_gid();
 435                 wq->pid = pid;
 436                 wq->tgid = tgid;
 437                 wq->status = -EINTR; /* Status return if interrupted */
 438                 wq->wait_ctr = 2;
 439
 440                 if (sbi->version < 5) {
 441                         if (notify == NFY_MOUNT)
 442                                 type = autofs_ptype_missing;
 443                         else
 444                                 type = autofs_ptype_expire_multi;
 445                 } else {
 446                         if (notify == NFY_MOUNT)
 447                                 type = autofs_type_trigger(sbi->type) ?
 448                                         autofs_ptype_missing_direct :
 449                                          autofs_ptype_missing_indirect;
 450                         else
 451                                 type = autofs_type_trigger(sbi->type) ?
 452                                         autofs_ptype_expire_direct :
 453                                         autofs_ptype_expire_indirect;
 454                 }
 455
 456                 pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 457                          (unsigned long) wq->wait_queue_token, wq->name.len,
 458                          wq->name.name, notify);
 459
 460                 /*
 461                  * autofs4_notify_daemon() may block; it will unlock ->wq_mutex
 462                  */
 463                 autofs4_notify_daemon(sbi, wq, type);
 464         } else {
 465                 wq->wait_ctr++;
 466                 pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 467                          (unsigned long) wq->wait_queue_token, wq->name.len,
 468                          wq->name.name, notify);
 469                 mutex_unlock(&sbi->wq_mutex);
 470                 kfree(qstr.name);
 471         }
 472
 473         /*
 474          * wq->name.name is NULL iff the lock is already released
 475          * or the mount has been made catatonic.
 476          */
 477         if (wq->name.name) {
 478                 /* Block all but "shutdown" signals while waiting */
 479                 unsigned long shutdown_sigs_mask;
 480                 unsigned long irqflags;
 481                 sigset_t oldset;
 482
 483                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 484                 oldset = current->blocked;
 485                 shutdown_sigs_mask = SHUTDOWN_SIGS & ~oldset.sig[0];
 486                 siginitsetinv(&current->blocked, shutdown_sigs_mask);
 487                 recalc_sigpending();
 488                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 489
 490                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 491
 492                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 493                 current->blocked = oldset;
 494                 recalc_sigpending();
 495                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 496         } else {
 497                 pr_debug("skipped sleeping\n");
 498         }
 499
 500         status = wq->status;
 501
 502         /*
 503          * For direct and offset mounts we need to track the requester's
 504          * uid and gid in the dentry info struct. This is so it can be
 505          * supplied, on request, by the misc device ioctl interface.
 506          * This is needed during daemon resatart when reconnecting
 507          * to existing, active, autofs mounts. The uid and gid (and
 508          * related string values) may be used for macro substitution
 509          * in autofs mount maps.
 510          */
 511         if (!status) {
 512                 struct autofs_info *ino;
 513                 struct dentry *de = NULL;
 514
 515                 /* direct mount or browsable map */
 516                 ino = autofs4_dentry_ino(dentry);
 517                 if (!ino) {
 518                         /* If not lookup actual dentry used */
 519                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 520                         if (de)
 521                                 ino = autofs4_dentry_ino(de);
 522                 }
 523
 524                 /* Set mount requester */
 525                 if (ino) {
 526                         spin_lock(&sbi->fs_lock);
 527                         ino->uid = wq->uid;
 528                         ino->gid = wq->gid;
 529                         spin_unlock(&sbi->fs_lock);
 530                 }
 531
 532                 if (de)
 533                         dput(de);
 534         }
 535
 536         /* Are we the last process to need status? */
 537         mutex_lock(&sbi->wq_mutex);
 538         if (!--wq->wait_ctr)
 539                 kfree(wq);
 540         mutex_unlock(&sbi->wq_mutex);
 541
 542         return status;
 543 }
 544
 545
 546 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 547 {
 548         struct autofs_wait_queue *wq, **wql;
 549
 550         mutex_lock(&sbi->wq_mutex);
 551         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 552                 if (wq->wait_queue_token == wait_queue_token)
 553                         break;
 554         }
 555
 556         if (!wq) {
 557                 mutex_unlock(&sbi->wq_mutex);
 558                 return -EINVAL;
 559         }
 560
 561         *wql = wq->next;        /* Unlink from chain */
 562         kfree(wq->name.name);
 563         wq->name.name = NULL;   /* Do not wait on this queue */
 564         wq->status = status;
 565         wake_up_interruptible(&wq->queue);
 566         if (!--wq->wait_ctr)
 567                 kfree(wq);
 568         mutex_unlock(&sbi->wq_mutex);
 569
 570         return 0;
 571 }