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 = file->f_op->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         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         DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
 106                 (unsigned long) wq->wait_queue_token, 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 = &pkt.v4_pkt.expire_multi;
 130
 131                 pktsz = sizeof(*ep);
 132
 133                 ep->wait_queue_token = wq->wait_queue_token;
 134                 ep->len = wq->name.len;
 135                 memcpy(ep->name, wq->name.name, wq->name.len);
 136                 ep->name[wq->name.len] = '\0';
 137                 break;
 138         }
 139         /*
 140          * Kernel protocol v5 packet for handling indirect and direct
 141          * mount missing and expire requests
 142          */
 143         case autofs_ptype_missing_indirect:
 144         case autofs_ptype_expire_indirect:
 145         case autofs_ptype_missing_direct:
 146         case autofs_ptype_expire_direct:
 147         {
 148                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 149                 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
 150
 151                 pktsz = sizeof(*packet);
 152
 153                 packet->wait_queue_token = wq->wait_queue_token;
 154                 packet->len = wq->name.len;
 155                 memcpy(packet->name, wq->name.name, wq->name.len);
 156                 packet->name[wq->name.len] = '\0';
 157                 packet->dev = wq->dev;
 158                 packet->ino = wq->ino;
 159                 packet->uid = from_kuid_munged(user_ns, wq->uid);
 160                 packet->gid = from_kgid_munged(user_ns, wq->gid);
 161                 packet->pid = wq->pid;
 162                 packet->tgid = wq->tgid;
 163                 break;
 164         }
 165         default:
 166                 printk("autofs4_notify_daemon: bad type %d!\n", type);
 167                 mutex_unlock(&sbi->wq_mutex);
 168                 return;
 169         }
 170
 171         pipe = get_file(sbi->pipe);
 172
 173         mutex_unlock(&sbi->wq_mutex);
 174
 175         if (autofs4_write(sbi, pipe, &pkt, pktsz))
 176                 autofs4_catatonic_mode(sbi);
 177         fput(pipe);
 178 }
 179
 180 static int autofs4_getpath(struct autofs_sb_info *sbi,
 181                            struct dentry *dentry, char **name)
 182 {
 183         struct dentry *root = sbi->sb->s_root;
 184         struct dentry *tmp;
 185         char *buf;
 186         char *p;
 187         int len;
 188         unsigned seq;
 189
 190 rename_retry:
 191         buf = *name;
 192         len = 0;
 193
 194         seq = read_seqbegin(&rename_lock);
 195         rcu_read_lock();
 196         spin_lock(&sbi->fs_lock);
 197         for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
 198                 len += tmp->d_name.len + 1;
 199
 200         if (!len || --len > NAME_MAX) {
 201                 spin_unlock(&sbi->fs_lock);
 202                 rcu_read_unlock();
 203                 if (read_seqretry(&rename_lock, seq))
 204                         goto rename_retry;
 205                 return 0;
 206         }
 207
 208         *(buf + len) = '\0';
 209         p = buf + len - dentry->d_name.len;
 210         strncpy(p, dentry->d_name.name, dentry->d_name.len);
 211
 212         for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
 213                 *(--p) = '/';
 214                 p -= tmp->d_name.len;
 215                 strncpy(p, tmp->d_name.name, tmp->d_name.len);
 216         }
 217         spin_unlock(&sbi->fs_lock);
 218         rcu_read_unlock();
 219         if (read_seqretry(&rename_lock, seq))
 220                 goto rename_retry;
 221
 222         return len;
 223 }
 224
 225 static struct autofs_wait_queue *
 226 autofs4_find_wait(struct autofs_sb_info *sbi, struct qstr *qstr)
 227 {
 228         struct autofs_wait_queue *wq;
 229
 230         for (wq = sbi->queues; wq; wq = wq->next) {
 231                 if (wq->name.hash == qstr->hash &&
 232                     wq->name.len == qstr->len &&
 233                     wq->name.name &&
 234                          !memcmp(wq->name.name, qstr->name, qstr->len))
 235                         break;
 236         }
 237         return wq;
 238 }
 239
 240 /*
 241  * Check if we have a valid request.
 242  * Returns
 243  * 1 if the request should continue.
 244  *   In this case we can return an autofs_wait_queue entry if one is
 245  *   found or NULL to idicate a new wait needs to be created.
 246  * 0 or a negative errno if the request shouldn't continue.
 247  */
 248 static int validate_request(struct autofs_wait_queue **wait,
 249                             struct autofs_sb_info *sbi,
 250                             struct qstr *qstr,
 251                             struct dentry*dentry, enum autofs_notify notify)
 252 {
 253         struct autofs_wait_queue *wq;
 254         struct autofs_info *ino;
 255
 256         if (sbi->catatonic)
 257                 return -ENOENT;
 258
 259         /* Wait in progress, continue; */
 260         wq = autofs4_find_wait(sbi, qstr);
 261         if (wq) {
 262                 *wait = wq;
 263                 return 1;
 264         }
 265
 266         *wait = NULL;
 267
 268         /* If we don't yet have any info this is a new request */
 269         ino = autofs4_dentry_ino(dentry);
 270         if (!ino)
 271                 return 1;
 272
 273         /*
 274          * If we've been asked to wait on an existing expire (NFY_NONE)
 275          * but there is no wait in the queue ...
 276          */
 277         if (notify == NFY_NONE) {
 278                 /*
 279                  * Either we've betean the pending expire to post it's
 280                  * wait or it finished while we waited on the mutex.
 281                  * So we need to wait till either, the wait appears
 282                  * or the expire finishes.
 283                  */
 284
 285                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 286                         mutex_unlock(&sbi->wq_mutex);
 287                         schedule_timeout_interruptible(HZ/10);
 288                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 289                                 return -EINTR;
 290
 291                         if (sbi->catatonic)
 292                                 return -ENOENT;
 293
 294                         wq = autofs4_find_wait(sbi, qstr);
 295                         if (wq) {
 296                                 *wait = wq;
 297                                 return 1;
 298                         }
 299                 }
 300
 301                 /*
 302                  * Not ideal but the status has already gone. Of the two
 303                  * cases where we wait on NFY_NONE neither depend on the
 304                  * return status of the wait.
 305                  */
 306                 return 0;
 307         }
 308
 309         /*
 310          * If we've been asked to trigger a mount and the request
 311          * completed while we waited on the mutex ...
 312          */
 313         if (notify == NFY_MOUNT) {
 314                 struct dentry *new = NULL;
 315                 int valid = 1;
 316
 317                 /*
 318                  * If the dentry was successfully mounted while we slept
 319                  * on the wait queue mutex we can return success. If it
 320                  * isn't mounted (doesn't have submounts for the case of
 321                  * a multi-mount with no mount at it's base) we can
 322                  * continue on and create a new request.
 323                  */
 324                 if (!IS_ROOT(dentry)) {
 325                         if (dentry->d_inode && d_unhashed(dentry)) {
 326                                 struct dentry *parent = dentry->d_parent;
 327                                 new = d_lookup(parent, &dentry->d_name);
 328                                 if (new)
 329                                         dentry = new;
 330                         }
 331                 }
 332                 if (have_submounts(dentry))
 333                         valid = 0;
 334
 335                 if (new)
 336                         dput(new);
 337                 return valid;
 338         }
 339
 340         return 1;
 341 }
 342
 343 int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
 344                 enum autofs_notify notify)
 345 {
 346         struct autofs_wait_queue *wq;
 347         struct qstr qstr;
 348         char *name;
 349         int status, ret, type;
 350         pid_t pid;
 351         pid_t tgid;
 352
 353         /* In catatonic mode, we don't wait for nobody */
 354         if (sbi->catatonic)
 355                 return -ENOENT;
 356
 357         /*
 358          * Try translating pids to the namespace of the daemon.
 359          *
 360          * Zero means failure: we are in an unrelated pid namespace.
 361          */
 362         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 363         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 364         if (pid == 0 || tgid == 0)
 365                 return -ENOENT;
 366
 367         if (!dentry->d_inode) {
 368                 /*
 369                  * A wait for a negative dentry is invalid for certain
 370                  * cases. A direct or offset mount "always" has its mount
 371                  * point directory created and so the request dentry must
 372                  * be positive or the map key doesn't exist. The situation
 373                  * is very similar for indirect mounts except only dentrys
 374                  * in the root of the autofs file system may be negative.
 375                  */
 376                 if (autofs_type_trigger(sbi->type))
 377                         return -ENOENT;
 378                 else if (!IS_ROOT(dentry->d_parent))
 379                         return -ENOENT;
 380         }
 381
 382         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 383         if (!name)
 384                 return -ENOMEM;
 385
 386         /* If this is a direct mount request create a dummy name */
 387         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type))
 388                 qstr.len = sprintf(name, "%p", dentry);
 389         else {
 390                 qstr.len = autofs4_getpath(sbi, dentry, &name);
 391                 if (!qstr.len) {
 392                         kfree(name);
 393                         return -ENOENT;
 394                 }
 395         }
 396         qstr.name = name;
 397         qstr.hash = full_name_hash(name, qstr.len);
 398
 399         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 400                 kfree(qstr.name);
 401                 return -EINTR;
 402         }
 403
 404         ret = validate_request(&wq, sbi, &qstr, dentry, notify);
 405         if (ret <= 0) {
 406                 if (ret != -EINTR)
 407                         mutex_unlock(&sbi->wq_mutex);
 408                 kfree(qstr.name);
 409                 return ret;
 410         }
 411
 412         if (!wq) {
 413                 /* Create a new wait queue */
 414                 wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
 415                 if (!wq) {
 416                         kfree(qstr.name);
 417                         mutex_unlock(&sbi->wq_mutex);
 418                         return -ENOMEM;
 419                 }
 420
 421                 wq->wait_queue_token = autofs4_next_wait_queue;
 422                 if (++autofs4_next_wait_queue == 0)
 423                         autofs4_next_wait_queue = 1;
 424                 wq->next = sbi->queues;
 425                 sbi->queues = wq;
 426                 init_waitqueue_head(&wq->queue);
 427                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 428                 wq->dev = autofs4_get_dev(sbi);
 429                 wq->ino = autofs4_get_ino(sbi);
 430                 wq->uid = current_uid();
 431                 wq->gid = current_gid();
 432                 wq->pid = pid;
 433                 wq->tgid = tgid;
 434                 wq->status = -EINTR; /* Status return if interrupted */
 435                 wq->wait_ctr = 2;
 436
 437                 if (sbi->version < 5) {
 438                         if (notify == NFY_MOUNT)
 439                                 type = autofs_ptype_missing;
 440                         else
 441                                 type = autofs_ptype_expire_multi;
 442                 } else {
 443                         if (notify == NFY_MOUNT)
 444                                 type = autofs_type_trigger(sbi->type) ?
 445                                         autofs_ptype_missing_direct :
 446                                          autofs_ptype_missing_indirect;
 447                         else
 448                                 type = autofs_type_trigger(sbi->type) ?
 449                                         autofs_ptype_expire_direct :
 450                                         autofs_ptype_expire_indirect;
 451                 }
 452
 453                 DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 454                         (unsigned long) wq->wait_queue_token, wq->name.len,
 455                         wq->name.name, notify);
 456
 457                 /* autofs4_notify_daemon() may block; it will unlock ->wq_mutex */
 458                 autofs4_notify_daemon(sbi, wq, type);
 459         } else {
 460                 wq->wait_ctr++;
 461                 DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
 462                         (unsigned long) wq->wait_queue_token, wq->name.len,
 463                         wq->name.name, notify);
 464                 mutex_unlock(&sbi->wq_mutex);
 465                 kfree(qstr.name);
 466         }
 467
 468         /*
 469          * wq->name.name is NULL iff the lock is already released
 470          * or the mount has been made catatonic.
 471          */
 472         if (wq->name.name) {
 473                 /* Block all but "shutdown" signals while waiting */
 474                 sigset_t oldset;
 475                 unsigned long irqflags;
 476
 477                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 478                 oldset = current->blocked;
 479                 siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
 480                 recalc_sigpending();
 481                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 482
 483                 wait_event_interruptible(wq->queue, wq->name.name == NULL);
 484
 485                 spin_lock_irqsave(&current->sighand->siglock, irqflags);
 486                 current->blocked = oldset;
 487                 recalc_sigpending();
 488                 spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
 489         } else {
 490                 DPRINTK("skipped sleeping");
 491         }
 492
 493         status = wq->status;
 494
 495         /*
 496          * For direct and offset mounts we need to track the requester's
 497          * uid and gid in the dentry info struct. This is so it can be
 498          * supplied, on request, by the misc device ioctl interface.
 499          * This is needed during daemon resatart when reconnecting
 500          * to existing, active, autofs mounts. The uid and gid (and
 501          * related string values) may be used for macro substitution
 502          * in autofs mount maps.
 503          */
 504         if (!status) {
 505                 struct autofs_info *ino;
 506                 struct dentry *de = NULL;
 507
 508                 /* direct mount or browsable map */
 509                 ino = autofs4_dentry_ino(dentry);
 510                 if (!ino) {
 511                         /* If not lookup actual dentry used */
 512                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 513                         if (de)
 514                                 ino = autofs4_dentry_ino(de);
 515                 }
 516
 517                 /* Set mount requester */
 518                 if (ino) {
 519                         spin_lock(&sbi->fs_lock);
 520                         ino->uid = wq->uid;
 521                         ino->gid = wq->gid;
 522                         spin_unlock(&sbi->fs_lock);
 523                 }
 524
 525                 if (de)
 526                         dput(de);
 527         }
 528
 529         /* Are we the last process to need status? */
 530         mutex_lock(&sbi->wq_mutex);
 531         if (!--wq->wait_ctr)
 532                 kfree(wq);
 533         mutex_unlock(&sbi->wq_mutex);
 534
 535         return status;
 536 }
 537
 538
 539 int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
 540 {
 541         struct autofs_wait_queue *wq, **wql;
 542
 543         mutex_lock(&sbi->wq_mutex);
 544         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 545                 if (wq->wait_queue_token == wait_queue_token)
 546                         break;
 547         }
 548
 549         if (!wq) {
 550                 mutex_unlock(&sbi->wq_mutex);
 551                 return -EINVAL;
 552         }
 553
 554         *wql = wq->next;        /* Unlink from chain */
 555         kfree(wq->name.name);
 556         wq->name.name = NULL;   /* Do not wait on this queue */
 557         wq->status = status;
 558         wake_up_interruptible(&wq->queue);
 559         if (!--wq->wait_ctr)
 560                 kfree(wq);
 561         mutex_unlock(&sbi->wq_mutex);
 562
 563         return 0;
 564 }
 565