fs/autofs4/waitq.c

   1 /* -*- c -*- --------------------------------------------------------------- *
   2  *
   3  * linux/fs/autofs/waitq.c
   4  *
   5  *  Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   6  *  Copyright 2001-2006 Ian Kent <raven@themaw.net>
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * ------------------------------------------------------------------------- */
  13
  14 #include <linux/slab.h>
  15 #include <linux/time.h>
  16 #include <linux/signal.h>
  17 #include <linux/file.h>
  18 #include "autofs_i.h"
  19
  20 /* We make this a static variable rather than a part of the superblock; it
  21    is better if we don't reassign numbers easily even across filesystems */
  22 static autofs_wqt_t autofs4_next_wait_queue = 1;
  23
  24 /* These are the signals we allow interrupting a pending mount */
  25 #define SHUTDOWN_SIGS   (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
  26
  27 void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
  28 {
  29         struct autofs_wait_queue *wq, *nwq;
  30
  31         mutex_lock(&sbi->wq_mutex);
  32         if (sbi->catatonic) {
  33                 mutex_unlock(&sbi->wq_mutex);
  34                 return;
  35         }
  36
  37         DPRINTK("entering catatonic mode");
  38
  39         sbi->catatonic = 1;
  40         wq = sbi->queues;
  41         sbi->queues = NULL;     /* Erase all wait queues */
  42         while (wq) {
  43                 nwq = wq->next;
  44                 wq->status = -ENOENT; /* Magic is gone - report failure */
  45                 kfree(wq->name.name);
  46                 wq->name.name = NULL;
  47                 wq->wait_ctr--;
  48                 wake_up_interruptible(&wq->queue);
  49                 wq = nwq;
  50         }
  51         fput(sbi->pipe);        /* Close the pipe */
  52         sbi->pipe = NULL;
  53         sbi->pipefd = -1;
  54         mutex_unlock(&sbi->wq_mutex);
  55 }
  56
  57 static int autofs4_write(struct autofs_sb_info *sbi,
  58                          struct file *file, const void *addr, int bytes)
  59 {
  60         unsigned long sigpipe, flags;
  61         mm_segment_t fs;
  62         const char *data = (const char *)addr;
  63         ssize_t wr = 0;
  64
  65         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  66
  67         /* Save pointer to user space and point back to kernel space */
  68         fs = get_fs();
  69         set_fs(KERNEL_DS);
  70
  71         mutex_lock(&sbi->pipe_mutex);
  72         while (bytes &&
  73                (wr = __vfs_write(file,data,bytes,&file->f_pos)) > 0) {
  74                 data += wr;
  75                 bytes -= wr;
  76         }
  77         mutex_unlock(&sbi->pipe_mutex);
  78
  79         set_fs(fs);
  80
  81         /* Keep the currently executing process from receiving a
  82            SIGPIPE unless it was already supposed to get one */
  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         /* if 'wr' returned 0 (impossible) we assume -EIO (safe) */
  91         return bytes == 0 ? 0 : wr < 0 ? wr : -EIO;
  92 }
  93
  94 static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
  95                                  struct autofs_wait_queue *wq,
  96                                  int type)
  97 {
  98         union {
  99                 struct autofs_packet_hdr hdr;
 100                 union autofs_packet_union v4_pkt;
 101                 union autofs_v5_packet_union v5_pkt;
 102         } pkt;
 103         struct file *pipe = NULL;
 104         size_t pktsz;
 105         int ret;
 106
 107         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 108                 (unsigned long) wq->wait_queue_token, wq->name.len, wq->name.name, type);
 109
 110         memset(&pkt,0,sizeof pkt); /* For security reasons */
 111
 112         pkt.hdr.proto_version = sbi->version;
 113         pkt.hdr.type = type;
 114
 115         switch (type) {
 116         /* Kernel protocol v4 missing and expire packets */
 117         case autofs_ptype_missing:
 118         {
 119                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 120
 121                 pktsz = sizeof(*mp);
 122
 123                 mp->wait_queue_token = wq->wait_queue_token;
 124                 mp->len = wq->name.len;
 125                 memcpy(mp->name, wq->name.name, wq->name.len);
 126                 mp->name[wq->name.len] = '\0';
 127                 break;
 128         }
 129         case autofs_ptype_expire_multi:
 130         {
 131                 struct autofs_packet_expire_multi *ep = &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                 printk("autofs4_notify_daemon: 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         switch (ret = autofs4_write(sbi, pipe, &pkt, pktsz)) {
 178         case 0:
 179                 break;
 180         case -ENOMEM:
 181         case -ERESTARTSYS:
 182                 /* Just fail this one */
 183                 autofs4_wait_release(sbi, wq->wait_queue_token, ret);
 184                 break;
 185         default:
 186                 autofs4_catatonic_mode(sbi);
 187                 break;
 188         }
 189         fput(pipe);
 190 }
 191
 192 static int autofs4_getpath(struct autofs_sb_info *sbi,
 193                            struct dentry *dentry, char **name)
 194 {
 195         struct dentry *root = sbi->sb->s_root;
 196         struct dentry *tmp;
 197         char *buf;
 198         char *p;
 199         int len;
 200         unsigned seq;
 201
 202 rename_retry:
 203         buf = *name;
 204         len = 0;
 205
 206         seq = read_seqbegin(&rename_lock);
 207         rcu_read_lock();
 208         spin_lock(&sbi->fs_lock);
 209         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 210                 len += tmp->d_name.len + 1;
 211
 212         if (!len || --len > NAME_MAX) {
 213                 spin_unlock(&sbi->fs_lock);
 214                 rcu_read_unlock();
 215                 if (read_seqretry(&rename_lock, seq))
 216                         goto rename_retry;
 217                 return 0;
 218         }
 219
 220         *(buf + len) = '\0';
 221         p = buf + len - dentry->d_name.len;
 222         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 223
 224         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 225                 *(--p) = '/';
 226                 p -= tmp->d_name.len;
 227                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 228         }
 229         spin_unlock(&sbi->fs_lock);
 230         rcu_read_unlock();
 231         if (read_seqretry(&rename_lock, seq))
 232                 goto rename_retry;
 233
 234         return len;
 235 }
 236
 237 static struct autofs_wait_queue *
 238 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 239 {
 240         struct autofs_wait_queue *wq;
 241
 242         for (wq = sbi->queues; wq; wq = wq->next) {
 243                 if (wq->name.hash == qstr->hash &&
 244                     wq->name.len == qstr->len &&
 245                     wq->name.name &&
 246                          !memcmp(wq->name.name, qstr->name, qstr->len))
 247                         break;
 248         }
 249         return wq;
 250 }
 251
 252 /*
 253  * Check if we have a valid request.
 254  * Returns
 255  * 1 if the request should continue.
 256  *   In this case we can return an autofs_wait_queue entry if one is
 257  *   found or NULL to idicate a new wait needs to be created.
 258  * 0 or a negative errno if the request shouldn't continue.
 259  */
 260 static int validate_request(struct autofs_wait_queue **wait,
 261                             struct autofs_sb_info *sbi,
 262                             struct qstr *qstr,
 263                             struct dentry*dentry, enum autofs_notify notify)
 264 {
 265         struct autofs_wait_queue *wq;
 266         struct autofs_info *ino;
 267
 268         if (sbi->catatonic)
 269                 return -ENOENT;
 270
 271         /* Wait in progress, continue; */
 272         wq = autofs4_find_wait(sbi, qstr);
 273         if (wq) {
 274                 *wait = wq;
 275                 return 1;
 276         }
 277
 278         *wait = NULL;
 279
 280         /* If we don't yet have any info this is a new request */
 281         ino = autofs4_dentry_ino(dentry);
 282         if (!ino)
 283                 return 1;
 284
 285         /*
 286          * If we've been asked to wait on an existing expire (NFY_NONE)
 287          * but there is no wait in the queue ...
 288          */
 289         if (notify == NFY_NONE) {
 290                 /*
 291                  * Either we've betean the pending expire to post it's
 292                  * wait or it finished while we waited on the mutex.
 293                  * So we need to wait till either, the wait appears
 294                  * or the expire finishes.
 295                  */
 296
 297                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 298                         mutex_unlock(&sbi->wq_mutex);
 299                         schedule_timeout_interruptible(HZ/10);
 300                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 301                                 return -EINTR;
 302
 303                         if (sbi->catatonic)
 304                                 return -ENOENT;
 305
 306                         wq = autofs4_find_wait(sbi, qstr);
 307                         if (wq) {
 308                                 *wait = wq;
 309                                 return 1;
 310                         }
 311                 }
 312
 313                 /*
 314                  * Not ideal but the status has already gone. Of the two
 315                  * cases where we wait on NFY_NONE neither depend on the
 316                  * return status of the wait.
 317                  */
 318                 return 0;
 319         }
 320
 321         /*
 322          * If we've been asked to trigger a mount and the request
 323          * completed while we waited on the mutex ...
 324          */
 325         if (notify == NFY_MOUNT) {
 326                 struct dentry *new = NULL;
 327                 int valid = 1;
 328
 329                 /*
 330                  * If the dentry was successfully mounted while we slept
 331                  * on the wait queue mutex we can return success. If it
 332                  * isn't mounted (doesn't have submounts for the case of
 333                  * a multi-mount with no mount at it's base) we can
 334                  * continue on and create a new request.
 335                  */
 336                 if (!IS_ROOT(dentry)) {
 337                         if (d_really_is_positive(dentry) && d_unhashed(dentry)) {
 338                                 struct dentry *parent = dentry->d_parent;
 339                                 new = d_lookup(parent, &dentry->d_name);
 340                                 if (new)
 341                                         dentry = new;
 342                         }
 343                 }
 344                 if (have_submounts(dentry))
 345                         valid = 0;
 346
 347                 if (new)
 348                         dput(new);
 349                 return valid;
 350         }
 351
 352         return 1;
 353 }
 354
 355 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 356                 enum autofs_notify notify)
 357 {
 358         struct autofs_wait_queue *wq;
 359         struct qstr qstr;
 360         char *name;
 361         int status, ret, type;
 362         pid_t pid;
 363         pid_t tgid;
 364
 365         /* In catatonic mode, we don't wait for nobody */
 366         if (sbi->catatonic)
 367                 return -ENOENT;
 368
 369         /*
 370          * Try translating pids to the namespace of the daemon.
 371          *
 372          * Zero means failure: we are in an unrelated pid namespace.
 373          */
 374         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 375         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 376         if (pid == 0 || tgid == 0)
 377                 return -ENOENT;
 378
 379         if (d_really_is_negative(dentry)) {
 380                 /*
 381                  * A wait for a negative dentry is invalid for certain
 382                  * cases. A direct or offset mount "always" has its mount
 383                  * point directory created and so the request dentry must
 384                  * be positive or the map key doesn't exist. The situation
 385                  * is very similar for indirect mounts except only dentrys
 386                  * in the root of the autofs file system may be negative.
 387                  */
 388                 if (autofs_type_trigger(sbi->type))
 389                         return -ENOENT;
 390                 else if (!IS_ROOT(dentry->d_parent))
 391                         return -ENOENT;
 392         }
 393
 394         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 395         if (!name)
 396                 return -ENOMEM;
 397
 398         /* If this is a direct mount request create a dummy name */
 399         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 400                 qstr.len = sprintf(name, "%p", dentry);
 401         else {
 402                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 403                 if (!qstr.len) {
 404                         kfree(name);
 405                         return -ENOENT;
 406                 }
 407         }
 408         qstr.name = name;
 409         qstr.hash = full_name_hash(name, qstr.len);
 410
 411         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 412                 kfree(qstr.name);
 413                 return -EINTR;
 414         }
 415
 416         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 417         if (ret <= 0) {
 418                 if (ret != -EINTR)
 419                         mutex_unlock(&sbi->wq_mutex);
 420                 kfree(qstr.name);
 421                 return ret;
 422         }
 423
 424         if (!wq) {
 425                 /* Create a new wait queue */
 426                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 427                 if (!wq) {
 428                         kfree(qstr.name);
 429                         mutex_unlock(&sbi->wq_mutex);
 430                         return -ENOMEM;
 431                 }
 432
 433                 wq->wait_queue_token = autofs4_next_wait_queue;
 434                 if (++autofs4_next_wait_queue == 0)
 435                         autofs4_next_wait_queue = 1;
 436                 wq->next = sbi->queues;
 437                 sbi->queues = wq;
 438                 init_waitqueue_head(&wq->queue);
 439                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 440                 wq->dev = autofs4_get_dev(sbi);
 441                 wq->ino = autofs4_get_ino(sbi);
 442                 wq->uid = current_uid();
 443                 wq->gid = current_gid();
 444                 wq->pid = pid;
 445                 wq->tgid = tgid;
 446                 wq->status = -EINTR; /* Status return if interrupted */
 447                 wq->wait_ctr = 2;
 448
 449                 if (sbi->version < 5) {
 450                         if (notify == NFY_MOUNT)
 451                                 type = autofs_ptype_missing;
 452                         else
 453                                 type = autofs_ptype_expire_multi;
 454                 } else {
 455                         if (notify == NFY_MOUNT)
 456                                 type = autofs_type_trigger(sbi->type) ?
 457                                         autofs_ptype_missing_direct :
 458                                          autofs_ptype_missing_indirect;
 459                         else
 460                                 type = autofs_type_trigger(sbi->type) ?
 461                                         autofs_ptype_expire_direct :
 462                                         autofs_ptype_expire_indirect;
 463                 }
 464
 465                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 466                         (unsigned long) wq->wait_queue_token, wq->name.len,
 467                         wq->name.name, notify);
 468
 469                 /* autofs4_notify_daemon() may block; it will unlock ->wq_mutex */
 470                 autofs4_notify_daemon(sbi, wq, type);
 471         } else {
 472                 wq->wait_ctr++;
 473                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 474                         (unsigned long) wq->wait_queue_token, wq->name.len,
 475                         wq->name.name, notify);
 476                 mutex_unlock(&sbi->wq_mutex);
 477                 kfree(qstr.name);
 478         }
 479
 480         /*
 481          * wq->name.name is NULL iff the lock is already released
 482          * or the mount has been made catatonic.
 483          */
 484         if (wq->name.name) {
 485                 /* Block all but "shutdown" signals while waiting */
 486                 sigset_t oldset;
 487                 unsigned long irqflags;
 488
 489                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 490                 oldset = current->blocked;
 491                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 492                 recalc_sigpending();
 493                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 494
 495                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 496
 497                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 498                 current->blocked = oldset;
 499                 recalc_sigpending();
 500                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 501         } else {
 502                 DPRINTK("skipped sleeping");
 503         }
 504
 505         status = wq->status;
 506
 507         /*
 508          * For direct and offset mounts we need to track the requester's
 509          * uid and gid in the dentry info struct. This is so it can be
 510          * supplied, on request, by the misc device ioctl interface.
 511          * This is needed during daemon resatart when reconnecting
 512          * to existing, active, autofs mounts. The uid and gid (and
 513          * related string values) may be used for macro substitution
 514          * in autofs mount maps.
 515          */
 516         if (!status) {
 517                 struct autofs_info *ino;
 518                 struct dentry *de = NULL;
 519
 520                 /* direct mount or browsable map */
 521                 ino = autofs4_dentry_ino(dentry);
 522                 if (!ino) {
 523                         /* If not lookup actual dentry used */
 524                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 525                         if (de)
 526                                 ino = autofs4_dentry_ino(de);
 527                 }
 528
 529                 /* Set mount requester */
 530                 if (ino) {
 531                         spin_lock(&sbi->fs_lock);
 532                         ino->uid = wq->uid;
 533                         ino->gid = wq->gid;
 534                         spin_unlock(&sbi->fs_lock);
 535                 }
 536
 537                 if (de)
 538                         dput(de);
 539         }
 540
 541         /* Are we the last process to need status? */
 542         mutex_lock(&sbi->wq_mutex);
 543         if (!--wq->wait_ctr)
 544                 kfree(wq);
 545         mutex_unlock(&sbi->wq_mutex);
 546
 547         return status;
 548 }
 549
 550
 551 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 552 {
 553         struct autofs_wait_queue *wq, **wql;
 554
 555         mutex_lock(&sbi->wq_mutex);
 556         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 557                 if (wq->wait_queue_token == wait_queue_token)
 558                         break;
 559         }
 560
 561         if (!wq) {
 562                 mutex_unlock(&sbi->wq_mutex);
 563                 return -EINVAL;
 564         }
 565
 566         *wql = wq->next;        /* Unlink from chain */
 567         kfree(wq->name.name);
 568         wq->name.name = NULL;   /* Do not wait on this queue */
 569         wq->status = status;
 570         wake_up_interruptible(&wq->queue);
 571         if (!--wq->wait_ctr)
 572                 kfree(wq);
 573         mutex_unlock(&sbi->wq_mutex);
 574
 575         return 0;
 576 }
 577