fs/ecryptfs/miscdev.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  *
   4  * Copyright (C) 2008 International Business Machines Corp.
   5  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License version
   9  * 2 as published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19  * 02111-1307, USA.
  20  */
  21
  22 #include <linux/fs.h>
  23 #include <linux/hash.h>
  24 #include <linux/random.h>
  25 #include <linux/miscdevice.h>
  26 #include <linux/poll.h>
  27 #include <linux/slab.h>
  28 #include <linux/wait.h>
  29 #include <linux/module.h>
  30 #include "ecryptfs_kernel.h"
  31
  32 static atomic_t ecryptfs_num_miscdev_opens;
  33
  34 /**
  35  * ecryptfs_miscdev_poll
  36  * @file: dev file (ignored)
  37  * @pt: dev poll table (ignored)
  38  *
  39  * Returns the poll mask
  40  */
  41 static unsigned int
  42 ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
  43 {
  44         struct ecryptfs_daemon *daemon;
  45         unsigned int mask = 0;
  46         uid_t euid = current_euid();
  47         int rc;
  48
  49         mutex_lock(&ecryptfs_daemon_hash_mux);
  50         /* TODO: Just use file->private_data? */
  51         rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
  52         BUG_ON(rc || !daemon);
  53         mutex_lock(&daemon->mux);
  54         mutex_unlock(&ecryptfs_daemon_hash_mux);
  55         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
  56                 printk(KERN_WARNING "%s: Attempt to poll on zombified "
  57                        "daemon\n", __func__);
  58                 goto out_unlock_daemon;
  59         }
  60         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
  61                 goto out_unlock_daemon;
  62         if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
  63                 goto out_unlock_daemon;
  64         daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
  65         mutex_unlock(&daemon->mux);
  66         poll_wait(file, &daemon->wait, pt);
  67         mutex_lock(&daemon->mux);
  68         if (!list_empty(&daemon->msg_ctx_out_queue))
  69                 mask |= POLLIN | POLLRDNORM;
  70 out_unlock_daemon:
  71         daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
  72         mutex_unlock(&daemon->mux);
  73         return mask;
  74 }
  75
  76 /**
  77  * ecryptfs_miscdev_open
  78  * @inode: inode of miscdev handle (ignored)
  79  * @file: file for miscdev handle (ignored)
  80  *
  81  * Returns zero on success; non-zero otherwise
  82  */
  83 static int
  84 ecryptfs_miscdev_open(struct inode *inode, struct file *file)
  85 {
  86         struct ecryptfs_daemon *daemon = NULL;
  87         uid_t euid = current_euid();
  88         int rc;
  89
  90         mutex_lock(&ecryptfs_daemon_hash_mux);
  91         rc = try_module_get(THIS_MODULE);
  92         if (rc == 0) {
  93                 rc = -EIO;
  94                 printk(KERN_ERR "%s: Error attempting to increment module use "
  95                        "count; rc = [%d]\n", __func__, rc);
  96                 goto out_unlock_daemon_list;
  97         }
  98         rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
  99         if (rc || !daemon) {
 100                 rc = ecryptfs_spawn_daemon(&daemon, euid, current_user_ns(),
 101                                            task_pid(current));
 102                 if (rc) {
 103                         printk(KERN_ERR "%s: Error attempting to spawn daemon; "
 104                                "rc = [%d]\n", __func__, rc);
 105                         goto out_module_put_unlock_daemon_list;
 106                 }
 107         }
 108         mutex_lock(&daemon->mux);
 109         if (daemon->pid != task_pid(current)) {
 110                 rc = -EINVAL;
 111                 printk(KERN_ERR "%s: pid [0x%p] has registered with euid [%d], "
 112                        "but pid [0x%p] has attempted to open the handle "
 113                        "instead\n", __func__, daemon->pid, daemon->euid,
 114                        task_pid(current));
 115                 goto out_unlock_daemon;
 116         }
 117         if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
 118                 rc = -EBUSY;
 119                 printk(KERN_ERR "%s: Miscellaneous device handle may only be "
 120                        "opened once per daemon; pid [0x%p] already has this "
 121                        "handle open\n", __func__, daemon->pid);
 122                 goto out_unlock_daemon;
 123         }
 124         daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
 125         atomic_inc(&ecryptfs_num_miscdev_opens);
 126 out_unlock_daemon:
 127         mutex_unlock(&daemon->mux);
 128 out_module_put_unlock_daemon_list:
 129         if (rc)
 130                 module_put(THIS_MODULE);
 131 out_unlock_daemon_list:
 132         mutex_unlock(&ecryptfs_daemon_hash_mux);
 133         return rc;
 134 }
 135
 136 /**
 137  * ecryptfs_miscdev_release
 138  * @inode: inode of fs/ecryptfs/euid handle (ignored)
 139  * @file: file for fs/ecryptfs/euid handle (ignored)
 140  *
 141  * This keeps the daemon registered until the daemon sends another
 142  * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
 143  *
 144  * Returns zero on success; non-zero otherwise
 145  */
 146 static int
 147 ecryptfs_miscdev_release(struct inode *inode, struct file *file)
 148 {
 149         struct ecryptfs_daemon *daemon = NULL;
 150         uid_t euid = current_euid();
 151         int rc;
 152
 153         mutex_lock(&ecryptfs_daemon_hash_mux);
 154         rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
 155         BUG_ON(rc || !daemon);
 156         mutex_lock(&daemon->mux);
 157         BUG_ON(daemon->pid != task_pid(current));
 158         BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
 159         daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
 160         atomic_dec(&ecryptfs_num_miscdev_opens);
 161         mutex_unlock(&daemon->mux);
 162         rc = ecryptfs_exorcise_daemon(daemon);
 163         if (rc) {
 164                 printk(KERN_CRIT "%s: Fatal error whilst attempting to "
 165                        "shut down daemon; rc = [%d]. Please report this "
 166                        "bug.\n", __func__, rc);
 167                 BUG();
 168         }
 169         module_put(THIS_MODULE);
 170         mutex_unlock(&ecryptfs_daemon_hash_mux);
 171         return rc;
 172 }
 173
 174 /**
 175  * ecryptfs_send_miscdev
 176  * @data: Data to send to daemon; may be NULL
 177  * @data_size: Amount of data to send to daemon
 178  * @msg_ctx: Message context, which is used to handle the reply. If
 179  *           this is NULL, then we do not expect a reply.
 180  * @msg_type: Type of message
 181  * @msg_flags: Flags for message
 182  * @daemon: eCryptfs daemon object
 183  *
 184  * Add msg_ctx to queue and then, if it exists, notify the blocked
 185  * miscdevess about the data being available. Must be called with
 186  * ecryptfs_daemon_hash_mux held.
 187  *
 188  * Returns zero on success; non-zero otherwise
 189  */
 190 int ecryptfs_send_miscdev(char *data, size_t data_size,
 191                           struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
 192                           u16 msg_flags, struct ecryptfs_daemon *daemon)
 193 {
 194         int rc = 0;
 195
 196         mutex_lock(&msg_ctx->mux);
 197         msg_ctx->msg = kmalloc((sizeof(*msg_ctx->msg) + data_size),
 198                                GFP_KERNEL);
 199         if (!msg_ctx->msg) {
 200                 rc = -ENOMEM;
 201                 printk(KERN_ERR "%s: Out of memory whilst attempting "
 202                        "to kmalloc(%zd, GFP_KERNEL)\n", __func__,
 203                        (sizeof(*msg_ctx->msg) + data_size));
 204                 goto out_unlock;
 205         }
 206         msg_ctx->msg->index = msg_ctx->index;
 207         msg_ctx->msg->data_len = data_size;
 208         msg_ctx->type = msg_type;
 209         memcpy(msg_ctx->msg->data, data, data_size);
 210         msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
 211         mutex_lock(&daemon->mux);
 212         list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
 213         daemon->num_queued_msg_ctx++;
 214         wake_up_interruptible(&daemon->wait);
 215         mutex_unlock(&daemon->mux);
 216 out_unlock:
 217         mutex_unlock(&msg_ctx->mux);
 218         return rc;
 219 }
 220
 221 /*
 222  * miscdevfs packet format:
 223  *  Octet 0: Type
 224  *  Octets 1-4: network byte order msg_ctx->counter
 225  *  Octets 5-N0: Size of struct ecryptfs_message to follow
 226  *  Octets N0-N1: struct ecryptfs_message (including data)
 227  *
 228  *  Octets 5-N1 not written if the packet type does not include a message
 229  */
 230 #define PKT_TYPE_SIZE           1
 231 #define PKT_CTR_SIZE            4
 232 #define MIN_NON_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE)
 233 #define MIN_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
 234                                  + ECRYPTFS_MIN_PKT_LEN_SIZE)
 235 /* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
 236 #define MAX_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
 237                                  + ECRYPTFS_MAX_PKT_LEN_SIZE \
 238                                  + sizeof(struct ecryptfs_message) \
 239                                  + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
 240 #define PKT_TYPE_OFFSET         0
 241 #define PKT_CTR_OFFSET          PKT_TYPE_SIZE
 242 #define PKT_LEN_OFFSET          (PKT_TYPE_SIZE + PKT_CTR_SIZE)
 243
 244 /**
 245  * ecryptfs_miscdev_read - format and send message from queue
 246  * @file: fs/ecryptfs/euid miscdevfs handle (ignored)
 247  * @buf: User buffer into which to copy the next message on the daemon queue
 248  * @count: Amount of space available in @buf
 249  * @ppos: Offset in file (ignored)
 250  *
 251  * Pulls the most recent message from the daemon queue, formats it for
 252  * being sent via a miscdevfs handle, and copies it into @buf
 253  *
 254  * Returns the number of bytes copied into the user buffer
 255  */
 256 static ssize_t
 257 ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
 258                       loff_t *ppos)
 259 {
 260         struct ecryptfs_daemon *daemon;
 261         struct ecryptfs_msg_ctx *msg_ctx;
 262         size_t packet_length_size;
 263         char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
 264         size_t i;
 265         size_t total_length;
 266         uid_t euid = current_euid();
 267         int rc;
 268
 269         mutex_lock(&ecryptfs_daemon_hash_mux);
 270         /* TODO: Just use file->private_data? */
 271         rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
 272         BUG_ON(rc || !daemon);
 273         mutex_lock(&daemon->mux);
 274         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
 275                 rc = 0;
 276                 mutex_unlock(&ecryptfs_daemon_hash_mux);
 277                 printk(KERN_WARNING "%s: Attempt to read from zombified "
 278                        "daemon\n", __func__);
 279                 goto out_unlock_daemon;
 280         }
 281         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
 282                 rc = 0;
 283                 mutex_unlock(&ecryptfs_daemon_hash_mux);
 284                 goto out_unlock_daemon;
 285         }
 286         /* This daemon will not go away so long as this flag is set */
 287         daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
 288         mutex_unlock(&ecryptfs_daemon_hash_mux);
 289 check_list:
 290         if (list_empty(&daemon->msg_ctx_out_queue)) {
 291                 mutex_unlock(&daemon->mux);
 292                 rc = wait_event_interruptible(
 293                         daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
 294                 mutex_lock(&daemon->mux);
 295                 if (rc < 0) {
 296                         rc = 0;
 297                         goto out_unlock_daemon;
 298                 }
 299         }
 300         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
 301                 rc = 0;
 302                 goto out_unlock_daemon;
 303         }
 304         if (list_empty(&daemon->msg_ctx_out_queue)) {
 305                 /* Something else jumped in since the
 306                  * wait_event_interruptable() and removed the
 307                  * message from the queue; try again */
 308                 goto check_list;
 309         }
 310         BUG_ON(euid != daemon->euid);
 311         BUG_ON(current_user_ns() != daemon->user_ns);
 312         BUG_ON(task_pid(current) != daemon->pid);
 313         msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
 314                                    struct ecryptfs_msg_ctx, daemon_out_list);
 315         BUG_ON(!msg_ctx);
 316         mutex_lock(&msg_ctx->mux);
 317         if (msg_ctx->msg) {
 318                 rc = ecryptfs_write_packet_length(packet_length,
 319                                                   msg_ctx->msg_size,
 320                                                   &packet_length_size);
 321                 if (rc) {
 322                         rc = 0;
 323                         printk(KERN_WARNING "%s: Error writing packet length; "
 324                                "rc = [%d]\n", __func__, rc);
 325                         goto out_unlock_msg_ctx;
 326                 }
 327         } else {
 328                 packet_length_size = 0;
 329                 msg_ctx->msg_size = 0;
 330         }
 331         total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size
 332                         + msg_ctx->msg_size);
 333         if (count < total_length) {
 334                 rc = 0;
 335                 printk(KERN_WARNING "%s: Only given user buffer of "
 336                        "size [%zd], but we need [%zd] to read the "
 337                        "pending message\n", __func__, count, total_length);
 338                 goto out_unlock_msg_ctx;
 339         }
 340         rc = -EFAULT;
 341         if (put_user(msg_ctx->type, buf))
 342                 goto out_unlock_msg_ctx;
 343         if (put_user(cpu_to_be32(msg_ctx->counter),
 344                      (__be32 __user *)(&buf[PKT_CTR_OFFSET])))
 345                 goto out_unlock_msg_ctx;
 346         i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
 347         if (msg_ctx->msg) {
 348                 if (copy_to_user(&buf[i], packet_length, packet_length_size))
 349                         goto out_unlock_msg_ctx;
 350                 i += packet_length_size;
 351                 if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
 352                         goto out_unlock_msg_ctx;
 353                 i += msg_ctx->msg_size;
 354         }
 355         rc = i;
 356         list_del(&msg_ctx->daemon_out_list);
 357         kfree(msg_ctx->msg);
 358         msg_ctx->msg = NULL;
 359         /* We do not expect a reply from the userspace daemon for any
 360          * message type other than ECRYPTFS_MSG_REQUEST */
 361         if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
 362                 ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 363 out_unlock_msg_ctx:
 364         mutex_unlock(&msg_ctx->mux);
 365 out_unlock_daemon:
 366         daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
 367         mutex_unlock(&daemon->mux);
 368         return rc;
 369 }
 370
 371 /**
 372  * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
 373  * @data: Bytes comprising struct ecryptfs_message
 374  * @data_size: sizeof(struct ecryptfs_message) + data len
 375  * @euid: Effective user id of miscdevess sending the miscdev response
 376  * @user_ns: The namespace in which @euid applies
 377  * @pid: Miscdevess id of miscdevess sending the miscdev response
 378  * @seq: Sequence number for miscdev response packet
 379  *
 380  * Returns zero on success; non-zero otherwise
 381  */
 382 static int ecryptfs_miscdev_response(char *data, size_t data_size,
 383                                      uid_t euid, struct user_namespace *user_ns,
 384                                      struct pid *pid, u32 seq)
 385 {
 386         struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
 387         int rc;
 388
 389         if ((sizeof(*msg) + msg->data_len) != data_size) {
 390                 printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
 391                        "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
 392                        (sizeof(*msg) + msg->data_len), data_size);
 393                 rc = -EINVAL;
 394                 goto out;
 395         }
 396         rc = ecryptfs_process_response(msg, euid, user_ns, pid, seq);
 397         if (rc)
 398                 printk(KERN_ERR
 399                        "Error processing response message; rc = [%d]\n", rc);
 400 out:
 401         return rc;
 402 }
 403
 404 /**
 405  * ecryptfs_miscdev_write - handle write to daemon miscdev handle
 406  * @file: File for misc dev handle (ignored)
 407  * @buf: Buffer containing user data
 408  * @count: Amount of data in @buf
 409  * @ppos: Pointer to offset in file (ignored)
 410  *
 411  * Returns the number of bytes read from @buf
 412  */
 413 static ssize_t
 414 ecryptfs_miscdev_write(struct file *file, const char __user *buf,
 415                        size_t count, loff_t *ppos)
 416 {
 417         __be32 counter_nbo;
 418         u32 seq;
 419         size_t packet_size, packet_size_length;
 420         char *data;
 421         uid_t euid = current_euid();
 422         unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
 423         ssize_t rc;
 424
 425         if (count == 0) {
 426                 return 0;
 427         } else if (count == MIN_NON_MSG_PKT_SIZE) {
 428                 /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
 429                 goto memdup;
 430         } else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
 431                 printk(KERN_WARNING "%s: Acceptable packet size range is "
 432                        "[%d-%zu], but amount of data written is [%zu].",
 433                        __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
 434                 return -EINVAL;
 435         }
 436
 437         if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
 438                            sizeof(packet_size_peek))) {
 439                 printk(KERN_WARNING "%s: Error while inspecting packet size\n",
 440                        __func__);
 441                 return -EFAULT;
 442         }
 443
 444         rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
 445                                           &packet_size_length);
 446         if (rc) {
 447                 printk(KERN_WARNING "%s: Error parsing packet length; "
 448                        "rc = [%zd]\n", __func__, rc);
 449                 return rc;
 450         }
 451
 452         if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
 453             != count) {
 454                 printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
 455                        packet_size);
 456                 return -EINVAL;
 457         }
 458
 459 memdup:
 460         data = memdup_user(buf, count);
 461         if (IS_ERR(data)) {
 462                 printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
 463                        __func__, PTR_ERR(data));
 464                 return PTR_ERR(data);
 465         }
 466         switch (data[PKT_TYPE_OFFSET]) {
 467         case ECRYPTFS_MSG_RESPONSE:
 468                 if (count < (MIN_MSG_PKT_SIZE
 469                              + sizeof(struct ecryptfs_message))) {
 470                         printk(KERN_WARNING "%s: Minimum acceptable packet "
 471                                "size is [%zd], but amount of data written is "
 472                                "only [%zd]. Discarding response packet.\n",
 473                                __func__,
 474                                (MIN_MSG_PKT_SIZE
 475                                 + sizeof(struct ecryptfs_message)), count);
 476                         rc = -EINVAL;
 477                         goto out_free;
 478                 }
 479                 memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
 480                 seq = be32_to_cpu(counter_nbo);
 481                 rc = ecryptfs_miscdev_response(
 482                                 &data[PKT_LEN_OFFSET + packet_size_length],
 483                                 packet_size, euid, current_user_ns(),
 484                                 task_pid(current), seq);
 485                 if (rc) {
 486                         printk(KERN_WARNING "%s: Failed to deliver miscdev "
 487                                "response to requesting operation; rc = [%zd]\n",
 488                                __func__, rc);
 489                         goto out_free;
 490                 }
 491                 break;
 492         case ECRYPTFS_MSG_HELO:
 493         case ECRYPTFS_MSG_QUIT:
 494                 break;
 495         default:
 496                 ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
 497                                 "message of unrecognized type [%d]\n",
 498                                 data[0]);
 499                 rc = -EINVAL;
 500                 goto out_free;
 501         }
 502         rc = count;
 503 out_free:
 504         kfree(data);
 505         return rc;
 506 }
 507
 508
 509 static const struct file_operations ecryptfs_miscdev_fops = {
 510         .open    = ecryptfs_miscdev_open,
 511         .poll    = ecryptfs_miscdev_poll,
 512         .read    = ecryptfs_miscdev_read,
 513         .write   = ecryptfs_miscdev_write,
 514         .release = ecryptfs_miscdev_release,
 515         .llseek  = noop_llseek,
 516 };
 517
 518 static struct miscdevice ecryptfs_miscdev = {
 519         .minor = MISC_DYNAMIC_MINOR,
 520         .name  = "ecryptfs",
 521         .fops  = &ecryptfs_miscdev_fops
 522 };
 523
 524 /**
 525  * ecryptfs_init_ecryptfs_miscdev
 526  *
 527  * Messages sent to the userspace daemon from the kernel are placed on
 528  * a queue associated with the daemon. The next read against the
 529  * miscdev handle by that daemon will return the oldest message placed
 530  * on the message queue for the daemon.
 531  *
 532  * Returns zero on success; non-zero otherwise
 533  */
 534 int __init ecryptfs_init_ecryptfs_miscdev(void)
 535 {
 536         int rc;
 537
 538         atomic_set(&ecryptfs_num_miscdev_opens, 0);
 539         rc = misc_register(&ecryptfs_miscdev);
 540         if (rc)
 541                 printk(KERN_ERR "%s: Failed to register miscellaneous device "
 542                        "for communications with userspace daemons; rc = [%d]\n",
 543                        __func__, rc);
 544         return rc;
 545 }
 546
 547 /**
 548  * ecryptfs_destroy_ecryptfs_miscdev
 549  *
 550  * All of the daemons must be exorcised prior to calling this
 551  * function.
 552  */
 553 void ecryptfs_destroy_ecryptfs_miscdev(void)
 554 {
 555         BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
 556         misc_deregister(&ecryptfs_miscdev);
 557 }