fs/autofs/waitq.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
   4  * Copyright 2001-2006 Ian Kent <raven@themaw.net>
   5  */
   6
   7 #include <linux/sched/signal.h>
   8 #include "autofs_i.h"
   9
  10 /* We make this a static variable rather than a part of the superblock; it
  11  * is better if we don't reassign numbers easily even across filesystems
  12  */
  13 static autofs_wqt_t autofs_next_wait_queue = 1;
  14
  15 void autofs_catatonic_mode(struct autofs_sb_info *sbi)
  16 {
  17         struct autofs_wait_queue *wq, *nwq;
  18
  19         mutex_lock(&sbi->wq_mutex);
  20         if (sbi->flags & AUTOFS_SBI_CATATONIC) {
  21                 mutex_unlock(&sbi->wq_mutex);
  22                 return;
  23         }
  24
  25         pr_debug("entering catatonic mode\n");
  26
  27         sbi->flags |= AUTOFS_SBI_CATATONIC;
  28         wq = sbi->queues;
  29         sbi->queues = NULL;     /* Erase all wait queues */
  30         while (wq) {
  31                 nwq = wq->next;
  32                 wq->status = -ENOENT; /* Magic is gone - report failure */
  33                 kfree(wq->name.name - wq->offset);
  34                 wq->name.name = NULL;
  35                 wake_up(&wq->queue);
  36                 if (!--wq->wait_ctr)
  37                         kfree(wq);
  38                 wq = nwq;
  39         }
  40         fput(sbi->pipe);        /* Close the pipe */
  41         sbi->pipe = NULL;
  42         sbi->pipefd = -1;
  43         mutex_unlock(&sbi->wq_mutex);
  44 }
  45
  46 static int autofs_write(struct autofs_sb_info *sbi,
  47                         struct file *file, const void *addr, int bytes)
  48 {
  49         unsigned long sigpipe, flags;
  50         const char *data = (const char *)addr;
  51         ssize_t wr = 0;
  52
  53         sigpipe = sigismember(&current->pending.signal, SIGPIPE);
  54
  55         mutex_lock(&sbi->pipe_mutex);
  56         while (bytes) {
  57                 wr = __kernel_write(file, data, bytes, NULL);
  58                 if (wr <= 0)
  59                         break;
  60                 data += wr;
  61                 bytes -= wr;
  62         }
  63         mutex_unlock(&sbi->pipe_mutex);
  64
  65         /* Keep the currently executing process from receiving a
  66          * SIGPIPE unless it was already supposed to get one
  67          */
  68         if (wr == -EPIPE && !sigpipe) {
  69                 spin_lock_irqsave(&current->sighand->siglock, flags);
  70                 sigdelset(&current->pending.signal, SIGPIPE);
  71                 recalc_sigpending();
  72                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
  73         }
  74
  75         /* if 'wr' returned 0 (impossible) we assume -EIO (safe) */
  76         return bytes == 0 ? 0 : wr < 0 ? wr : -EIO;
  77 }
  78
  79 static void autofs_notify_daemon(struct autofs_sb_info *sbi,
  80                                  struct autofs_wait_queue *wq,
  81                                  int type)
  82 {
  83         union {
  84                 struct autofs_packet_hdr hdr;
  85                 union autofs_packet_union v4_pkt;
  86                 union autofs_v5_packet_union v5_pkt;
  87         } pkt;
  88         struct file *pipe = NULL;
  89         size_t pktsz;
  90         int ret;
  91
  92         pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
  93                  (unsigned long) wq->wait_queue_token,
  94                  wq->name.len, wq->name.name, type);
  95
  96         memset(&pkt, 0, sizeof(pkt)); /* For security reasons */
  97
  98         pkt.hdr.proto_version = sbi->version;
  99         pkt.hdr.type = type;
 100
 101         switch (type) {
 102         /* Kernel protocol v4 missing and expire packets */
 103         case autofs_ptype_missing:
 104         {
 105                 struct autofs_packet_missing *mp = &pkt.v4_pkt.missing;
 106
 107                 pktsz = sizeof(*mp);
 108
 109                 mp->wait_queue_token = wq->wait_queue_token;
 110                 mp->len = wq->name.len;
 111                 memcpy(mp->name, wq->name.name, wq->name.len);
 112                 mp->name[wq->name.len] = '\0';
 113                 break;
 114         }
 115         case autofs_ptype_expire_multi:
 116         {
 117                 struct autofs_packet_expire_multi *ep =
 118                                         &pkt.v4_pkt.expire_multi;
 119
 120                 pktsz = sizeof(*ep);
 121
 122                 ep->wait_queue_token = wq->wait_queue_token;
 123                 ep->len = wq->name.len;
 124                 memcpy(ep->name, wq->name.name, wq->name.len);
 125                 ep->name[wq->name.len] = '\0';
 126                 break;
 127         }
 128         /*
 129          * Kernel protocol v5 packet for handling indirect and direct
 130          * mount missing and expire requests
 131          */
 132         case autofs_ptype_missing_indirect:
 133         case autofs_ptype_expire_indirect:
 134         case autofs_ptype_missing_direct:
 135         case autofs_ptype_expire_direct:
 136         {
 137                 struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet;
 138                 struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
 139
 140                 pktsz = sizeof(*packet);
 141
 142                 packet->wait_queue_token = wq->wait_queue_token;
 143                 packet->len = wq->name.len;
 144                 memcpy(packet->name, wq->name.name, wq->name.len);
 145                 packet->name[wq->name.len] = '\0';
 146                 packet->dev = wq->dev;
 147                 packet->ino = wq->ino;
 148                 packet->uid = from_kuid_munged(user_ns, wq->uid);
 149                 packet->gid = from_kgid_munged(user_ns, wq->gid);
 150                 packet->pid = wq->pid;
 151                 packet->tgid = wq->tgid;
 152                 break;
 153         }
 154         default:
 155                 pr_warn("bad type %d!\n", type);
 156                 mutex_unlock(&sbi->wq_mutex);
 157                 return;
 158         }
 159
 160         pipe = get_file(sbi->pipe);
 161
 162         mutex_unlock(&sbi->wq_mutex);
 163
 164         switch (ret = autofs_write(sbi, pipe, &pkt, pktsz)) {
 165         case 0:
 166                 break;
 167         case -ENOMEM:
 168         case -ERESTARTSYS:
 169                 /* Just fail this one */
 170                 autofs_wait_release(sbi, wq->wait_queue_token, ret);
 171                 break;
 172         default:
 173                 autofs_catatonic_mode(sbi);
 174                 break;
 175         }
 176         fput(pipe);
 177 }
 178
 179 static struct autofs_wait_queue *
 180 autofs_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
 181 {
 182         struct autofs_wait_queue *wq;
 183
 184         for (wq = sbi->queues; wq; wq = wq->next) {
 185                 if (wq->name.hash == qstr->hash &&
 186                     wq->name.len == qstr->len &&
 187                     wq->name.name &&
 188                     !memcmp(wq->name.name, qstr->name, qstr->len))
 189                         break;
 190         }
 191         return wq;
 192 }
 193
 194 /*
 195  * Check if we have a valid request.
 196  * Returns
 197  * 1 if the request should continue.
 198  *   In this case we can return an autofs_wait_queue entry if one is
 199  *   found or NULL to idicate a new wait needs to be created.
 200  * 0 or a negative errno if the request shouldn't continue.
 201  */
 202 static int validate_request(struct autofs_wait_queue **wait,
 203                             struct autofs_sb_info *sbi,
 204                             const struct qstr *qstr,
 205                             const struct path *path, enum autofs_notify notify)
 206 {
 207         struct dentry *dentry = path->dentry;
 208         struct autofs_wait_queue *wq;
 209         struct autofs_info *ino;
 210
 211         if (sbi->flags & AUTOFS_SBI_CATATONIC)
 212                 return -ENOENT;
 213
 214         /* Wait in progress, continue; */
 215         wq = autofs_find_wait(sbi, qstr);
 216         if (wq) {
 217                 *wait = wq;
 218                 return 1;
 219         }
 220
 221         *wait = NULL;
 222
 223         /* If we don't yet have any info this is a new request */
 224         ino = autofs_dentry_ino(dentry);
 225         if (!ino)
 226                 return 1;
 227
 228         /*
 229          * If we've been asked to wait on an existing expire (NFY_NONE)
 230          * but there is no wait in the queue ...
 231          */
 232         if (notify == NFY_NONE) {
 233                 /*
 234                  * Either we've betean the pending expire to post it's
 235                  * wait or it finished while we waited on the mutex.
 236                  * So we need to wait till either, the wait appears
 237                  * or the expire finishes.
 238                  */
 239
 240                 while (ino->flags & AUTOFS_INF_EXPIRING) {
 241                         mutex_unlock(&sbi->wq_mutex);
 242                         schedule_timeout_interruptible(HZ/10);
 243                         if (mutex_lock_interruptible(&sbi->wq_mutex))
 244                                 return -EINTR;
 245
 246                         if (sbi->flags & AUTOFS_SBI_CATATONIC)
 247                                 return -ENOENT;
 248
 249                         wq = autofs_find_wait(sbi, qstr);
 250                         if (wq) {
 251                                 *wait = wq;
 252                                 return 1;
 253                         }
 254                 }
 255
 256                 /*
 257                  * Not ideal but the status has already gone. Of the two
 258                  * cases where we wait on NFY_NONE neither depend on the
 259                  * return status of the wait.
 260                  */
 261                 return 0;
 262         }
 263
 264         /*
 265          * If we've been asked to trigger a mount and the request
 266          * completed while we waited on the mutex ...
 267          */
 268         if (notify == NFY_MOUNT) {
 269                 struct dentry *new = NULL;
 270                 struct path this;
 271                 int valid = 1;
 272
 273                 /*
 274                  * If the dentry was successfully mounted while we slept
 275                  * on the wait queue mutex we can return success. If it
 276                  * isn't mounted (doesn't have submounts for the case of
 277                  * a multi-mount with no mount at it's base) we can
 278                  * continue on and create a new request.
 279                  */
 280                 if (!IS_ROOT(dentry)) {
 281                         if (d_unhashed(dentry) &&
 282                             d_really_is_positive(dentry)) {
 283                                 struct dentry *parent = dentry->d_parent;
 284
 285                                 new = d_lookup(parent, &dentry->d_name);
 286                                 if (new)
 287                                         dentry = new;
 288                         }
 289                 }
 290                 this.mnt = path->mnt;
 291                 this.dentry = dentry;
 292                 if (path_has_submounts(&this))
 293                         valid = 0;
 294
 295                 if (new)
 296                         dput(new);
 297                 return valid;
 298         }
 299
 300         return 1;
 301 }
 302
 303 int autofs_wait(struct autofs_sb_info *sbi,
 304                  const struct path *path, enum autofs_notify notify)
 305 {
 306         struct dentry *dentry = path->dentry;
 307         struct autofs_wait_queue *wq;
 308         struct qstr qstr;
 309         char *name;
 310         int status, ret, type;
 311         unsigned int offset = 0;
 312         pid_t pid;
 313         pid_t tgid;
 314
 315         /* In catatonic mode, we don't wait for nobody */
 316         if (sbi->flags & AUTOFS_SBI_CATATONIC)
 317                 return -ENOENT;
 318
 319         /*
 320          * Try translating pids to the namespace of the daemon.
 321          *
 322          * Zero means failure: we are in an unrelated pid namespace.
 323          */
 324         pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 325         tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
 326         if (pid == 0 || tgid == 0)
 327                 return -ENOENT;
 328
 329         if (d_really_is_negative(dentry)) {
 330                 /*
 331                  * A wait for a negative dentry is invalid for certain
 332                  * cases. A direct or offset mount "always" has its mount
 333                  * point directory created and so the request dentry must
 334                  * be positive or the map key doesn't exist. The situation
 335                  * is very similar for indirect mounts except only dentrys
 336                  * in the root of the autofs file system may be negative.
 337                  */
 338                 if (autofs_type_trigger(sbi->type))
 339                         return -ENOENT;
 340                 else if (!IS_ROOT(dentry->d_parent))
 341                         return -ENOENT;
 342         }
 343
 344         name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
 345         if (!name)
 346                 return -ENOMEM;
 347
 348         /* If this is a direct mount request create a dummy name */
 349         if (IS_ROOT(dentry) && autofs_type_trigger(sbi->type)) {
 350                 qstr.name = name;
 351                 qstr.len = sprintf(name, "%p", dentry);
 352         } else {
 353                 char *p = dentry_path_raw(dentry, name, NAME_MAX);
 354                 if (IS_ERR(p)) {
 355                         kfree(name);
 356                         return -ENOENT;
 357                 }
 358                 qstr.name = ++p; // skip the leading slash
 359                 qstr.len = strlen(p);
 360                 offset = p - name;
 361         }
 362         qstr.hash = full_name_hash(dentry, qstr.name, qstr.len);
 363
 364         if (mutex_lock_interruptible(&sbi->wq_mutex)) {
 365                 kfree(name);
 366                 return -EINTR;
 367         }
 368
 369         ret = validate_request(&wq, sbi, &qstr, path, notify);
 370         if (ret <= 0) {
 371                 if (ret != -EINTR)
 372                         mutex_unlock(&sbi->wq_mutex);
 373                 kfree(name);
 374                 return ret;
 375         }
 376
 377         if (!wq) {
 378                 /* Create a new wait queue */
 379                 wq = kmalloc(sizeof(struct autofs_wait_queue), GFP_KERNEL);
 380                 if (!wq) {
 381                         kfree(name);
 382                         mutex_unlock(&sbi->wq_mutex);
 383                         return -ENOMEM;
 384                 }
 385
 386                 wq->wait_queue_token = autofs_next_wait_queue;
 387                 if (++autofs_next_wait_queue == 0)
 388                         autofs_next_wait_queue = 1;
 389                 wq->next = sbi->queues;
 390                 sbi->queues = wq;
 391                 init_waitqueue_head(&wq->queue);
 392                 memcpy(&wq->name, &qstr, sizeof(struct qstr));
 393                 wq->offset = offset;
 394                 wq->dev = autofs_get_dev(sbi);
 395                 wq->ino = autofs_get_ino(sbi);
 396                 wq->uid = current_uid();
 397                 wq->gid = current_gid();
 398                 wq->pid = pid;
 399                 wq->tgid = tgid;
 400                 wq->status = -EINTR; /* Status return if interrupted */
 401                 wq->wait_ctr = 2;
 402
 403                 if (sbi->version < 5) {
 404                         if (notify == NFY_MOUNT)
 405                                 type = autofs_ptype_missing;
 406                         else
 407                                 type = autofs_ptype_expire_multi;
 408                 } else {
 409                         if (notify == NFY_MOUNT)
 410                                 type = autofs_type_trigger(sbi->type) ?
 411                                         autofs_ptype_missing_direct :
 412                                          autofs_ptype_missing_indirect;
 413                         else
 414                                 type = autofs_type_trigger(sbi->type) ?
 415                                         autofs_ptype_expire_direct :
 416                                         autofs_ptype_expire_indirect;
 417                 }
 418
 419                 pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 420                          (unsigned long) wq->wait_queue_token, wq->name.len,
 421                          wq->name.name, notify);
 422
 423                 /*
 424                  * autofs_notify_daemon() may block; it will unlock ->wq_mutex
 425                  */
 426                 autofs_notify_daemon(sbi, wq, type);
 427         } else {
 428                 wq->wait_ctr++;
 429                 pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
 430                          (unsigned long) wq->wait_queue_token, wq->name.len,
 431                          wq->name.name, notify);
 432                 mutex_unlock(&sbi->wq_mutex);
 433                 kfree(name);
 434         }
 435
 436         /*
 437          * wq->name.name is NULL iff the lock is already released
 438          * or the mount has been made catatonic.
 439          */
 440         wait_event_killable(wq->queue, wq->name.name == NULL);
 441         status = wq->status;
 442
 443         /*
 444          * For direct and offset mounts we need to track the requester's
 445          * uid and gid in the dentry info struct. This is so it can be
 446          * supplied, on request, by the misc device ioctl interface.
 447          * This is needed during daemon resatart when reconnecting
 448          * to existing, active, autofs mounts. The uid and gid (and
 449          * related string values) may be used for macro substitution
 450          * in autofs mount maps.
 451          */
 452         if (!status) {
 453                 struct autofs_info *ino;
 454                 struct dentry *de = NULL;
 455
 456                 /* direct mount or browsable map */
 457                 ino = autofs_dentry_ino(dentry);
 458                 if (!ino) {
 459                         /* If not lookup actual dentry used */
 460                         de = d_lookup(dentry->d_parent, &dentry->d_name);
 461                         if (de)
 462                                 ino = autofs_dentry_ino(de);
 463                 }
 464
 465                 /* Set mount requester */
 466                 if (ino) {
 467                         spin_lock(&sbi->fs_lock);
 468                         ino->uid = wq->uid;
 469                         ino->gid = wq->gid;
 470                         spin_unlock(&sbi->fs_lock);
 471                 }
 472
 473                 if (de)
 474                         dput(de);
 475         }
 476
 477         /* Are we the last process to need status? */
 478         mutex_lock(&sbi->wq_mutex);
 479         if (!--wq->wait_ctr)
 480                 kfree(wq);
 481         mutex_unlock(&sbi->wq_mutex);
 482
 483         return status;
 484 }
 485
 486
 487 int autofs_wait_release(struct autofs_sb_info *sbi,
 488                         autofs_wqt_t wait_queue_token, int status)
 489 {
 490         struct autofs_wait_queue *wq, **wql;
 491
 492         mutex_lock(&sbi->wq_mutex);
 493         for (wql = &sbi->queues; (wq = *wql) != NULL; wql = &wq->next) {
 494                 if (wq->wait_queue_token == wait_queue_token)
 495                         break;
 496         }
 497
 498         if (!wq) {
 499                 mutex_unlock(&sbi->wq_mutex);
 500                 return -EINVAL;
 501         }
 502
 503         *wql = wq->next;        /* Unlink from chain */
 504         kfree(wq->name.name - wq->offset);
 505         wq->name.name = NULL;   /* Do not wait on this queue */
 506         wq->status = status;
 507         wake_up(&wq->queue);
 508         if (!--wq->wait_ctr)
 509                 kfree(wq);
 510         mutex_unlock(&sbi->wq_mutex);
 511
 512         return 0;
 513 }