fs/ecryptfs/miscdev.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /**
   3  * eCryptfs: Linux filesystem encryption layer
   4  *
   5  * Copyright (C) 2008 International Business Machines Corp.
   6  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   7  */
   8
   9 #include <linux/fs.h>
  10 #include <linux/hash.h>
  11 #include <linux/random.h>
  12 #include <linux/miscdevice.h>
  13 #include <linux/poll.h>
  14 #include <linux/slab.h>
  15 #include <linux/wait.h>
  16 #include <linux/module.h>
  17 #include "ecryptfs_kernel.h"
  18
  19 static atomic_t ecryptfs_num_miscdev_opens;
  20
  21 /**
  22  * ecryptfs_miscdev_poll
  23  * @file: dev file
  24  * @pt: dev poll table (ignored)
  25  *
  26  * Returns the poll mask
  27  */
  28 static __poll_t
  29 ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
  30 {
  31         struct ecryptfs_daemon *daemon = file->private_data;
  32         __poll_t mask = 0;
  33
  34         mutex_lock(&daemon->mux);
  35         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
  36                 printk(KERN_WARNING "%s: Attempt to poll on zombified "
  37                        "daemon\n", __func__);
  38                 goto out_unlock_daemon;
  39         }
  40         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
  41                 goto out_unlock_daemon;
  42         if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
  43                 goto out_unlock_daemon;
  44         daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
  45         mutex_unlock(&daemon->mux);
  46         poll_wait(file, &daemon->wait, pt);
  47         mutex_lock(&daemon->mux);
  48         if (!list_empty(&daemon->msg_ctx_out_queue))
  49                 mask |= EPOLLIN | EPOLLRDNORM;
  50 out_unlock_daemon:
  51         daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
  52         mutex_unlock(&daemon->mux);
  53         return mask;
  54 }
  55
  56 /**
  57  * ecryptfs_miscdev_open
  58  * @inode: inode of miscdev handle (ignored)
  59  * @file: file for miscdev handle
  60  *
  61  * Returns zero on success; non-zero otherwise
  62  */
  63 static int
  64 ecryptfs_miscdev_open(struct inode *inode, struct file *file)
  65 {
  66         struct ecryptfs_daemon *daemon = NULL;
  67         int rc;
  68
  69         mutex_lock(&ecryptfs_daemon_hash_mux);
  70         rc = ecryptfs_find_daemon_by_euid(&daemon);
  71         if (!rc) {
  72                 rc = -EINVAL;
  73                 goto out_unlock_daemon_list;
  74         }
  75         rc = ecryptfs_spawn_daemon(&daemon, file);
  76         if (rc) {
  77                 printk(KERN_ERR "%s: Error attempting to spawn daemon; "
  78                        "rc = [%d]\n", __func__, rc);
  79                 goto out_unlock_daemon_list;
  80         }
  81         mutex_lock(&daemon->mux);
  82         if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
  83                 rc = -EBUSY;
  84                 goto out_unlock_daemon;
  85         }
  86         daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
  87         file->private_data = daemon;
  88         atomic_inc(&ecryptfs_num_miscdev_opens);
  89 out_unlock_daemon:
  90         mutex_unlock(&daemon->mux);
  91 out_unlock_daemon_list:
  92         mutex_unlock(&ecryptfs_daemon_hash_mux);
  93         return rc;
  94 }
  95
  96 /**
  97  * ecryptfs_miscdev_release
  98  * @inode: inode of fs/ecryptfs/euid handle (ignored)
  99  * @file: file for fs/ecryptfs/euid handle
 100  *
 101  * This keeps the daemon registered until the daemon sends another
 102  * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
 103  *
 104  * Returns zero on success; non-zero otherwise
 105  */
 106 static int
 107 ecryptfs_miscdev_release(struct inode *inode, struct file *file)
 108 {
 109         struct ecryptfs_daemon *daemon = file->private_data;
 110         int rc;
 111
 112         mutex_lock(&daemon->mux);
 113         BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
 114         daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
 115         atomic_dec(&ecryptfs_num_miscdev_opens);
 116         mutex_unlock(&daemon->mux);
 117
 118         mutex_lock(&ecryptfs_daemon_hash_mux);
 119         rc = ecryptfs_exorcise_daemon(daemon);
 120         mutex_unlock(&ecryptfs_daemon_hash_mux);
 121         if (rc) {
 122                 printk(KERN_CRIT "%s: Fatal error whilst attempting to "
 123                        "shut down daemon; rc = [%d]. Please report this "
 124                        "bug.\n", __func__, rc);
 125                 BUG();
 126         }
 127         return rc;
 128 }
 129
 130 /**
 131  * ecryptfs_send_miscdev
 132  * @data: Data to send to daemon; may be NULL
 133  * @data_size: Amount of data to send to daemon
 134  * @msg_ctx: Message context, which is used to handle the reply. If
 135  *           this is NULL, then we do not expect a reply.
 136  * @msg_type: Type of message
 137  * @msg_flags: Flags for message
 138  * @daemon: eCryptfs daemon object
 139  *
 140  * Add msg_ctx to queue and then, if it exists, notify the blocked
 141  * miscdevess about the data being available. Must be called with
 142  * ecryptfs_daemon_hash_mux held.
 143  *
 144  * Returns zero on success; non-zero otherwise
 145  */
 146 int ecryptfs_send_miscdev(char *data, size_t data_size,
 147                           struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
 148                           u16 msg_flags, struct ecryptfs_daemon *daemon)
 149 {
 150         struct ecryptfs_message *msg;
 151
 152         msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
 153         if (!msg)
 154                 return -ENOMEM;
 155
 156         mutex_lock(&msg_ctx->mux);
 157         msg_ctx->msg = msg;
 158         msg_ctx->msg->index = msg_ctx->index;
 159         msg_ctx->msg->data_len = data_size;
 160         msg_ctx->type = msg_type;
 161         memcpy(msg_ctx->msg->data, data, data_size);
 162         msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
 163         list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
 164         mutex_unlock(&msg_ctx->mux);
 165
 166         mutex_lock(&daemon->mux);
 167         daemon->num_queued_msg_ctx++;
 168         wake_up_interruptible(&daemon->wait);
 169         mutex_unlock(&daemon->mux);
 170
 171         return 0;
 172 }
 173
 174 /*
 175  * miscdevfs packet format:
 176  *  Octet 0: Type
 177  *  Octets 1-4: network byte order msg_ctx->counter
 178  *  Octets 5-N0: Size of struct ecryptfs_message to follow
 179  *  Octets N0-N1: struct ecryptfs_message (including data)
 180  *
 181  *  Octets 5-N1 not written if the packet type does not include a message
 182  */
 183 #define PKT_TYPE_SIZE           1
 184 #define PKT_CTR_SIZE            4
 185 #define MIN_NON_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE)
 186 #define MIN_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
 187                                  + ECRYPTFS_MIN_PKT_LEN_SIZE)
 188 /* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
 189 #define MAX_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
 190                                  + ECRYPTFS_MAX_PKT_LEN_SIZE \
 191                                  + sizeof(struct ecryptfs_message) \
 192                                  + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
 193 #define PKT_TYPE_OFFSET         0
 194 #define PKT_CTR_OFFSET          PKT_TYPE_SIZE
 195 #define PKT_LEN_OFFSET          (PKT_TYPE_SIZE + PKT_CTR_SIZE)
 196
 197 /**
 198  * ecryptfs_miscdev_read - format and send message from queue
 199  * @file: miscdevfs handle
 200  * @buf: User buffer into which to copy the next message on the daemon queue
 201  * @count: Amount of space available in @buf
 202  * @ppos: Offset in file (ignored)
 203  *
 204  * Pulls the most recent message from the daemon queue, formats it for
 205  * being sent via a miscdevfs handle, and copies it into @buf
 206  *
 207  * Returns the number of bytes copied into the user buffer
 208  */
 209 static ssize_t
 210 ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
 211                       loff_t *ppos)
 212 {
 213         struct ecryptfs_daemon *daemon = file->private_data;
 214         struct ecryptfs_msg_ctx *msg_ctx;
 215         size_t packet_length_size;
 216         char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
 217         size_t i;
 218         size_t total_length;
 219         int rc;
 220
 221         mutex_lock(&daemon->mux);
 222         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
 223                 rc = 0;
 224                 printk(KERN_WARNING "%s: Attempt to read from zombified "
 225                        "daemon\n", __func__);
 226                 goto out_unlock_daemon;
 227         }
 228         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
 229                 rc = 0;
 230                 goto out_unlock_daemon;
 231         }
 232         /* This daemon will not go away so long as this flag is set */
 233         daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
 234 check_list:
 235         if (list_empty(&daemon->msg_ctx_out_queue)) {
 236                 mutex_unlock(&daemon->mux);
 237                 rc = wait_event_interruptible(
 238                         daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
 239                 mutex_lock(&daemon->mux);
 240                 if (rc < 0) {
 241                         rc = 0;
 242                         goto out_unlock_daemon;
 243                 }
 244         }
 245         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
 246                 rc = 0;
 247                 goto out_unlock_daemon;
 248         }
 249         if (list_empty(&daemon->msg_ctx_out_queue)) {
 250                 /* Something else jumped in since the
 251                  * wait_event_interruptable() and removed the
 252                  * message from the queue; try again */
 253                 goto check_list;
 254         }
 255         msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
 256                                    struct ecryptfs_msg_ctx, daemon_out_list);
 257         BUG_ON(!msg_ctx);
 258         mutex_lock(&msg_ctx->mux);
 259         if (msg_ctx->msg) {
 260                 rc = ecryptfs_write_packet_length(packet_length,
 261                                                   msg_ctx->msg_size,
 262                                                   &packet_length_size);
 263                 if (rc) {
 264                         rc = 0;
 265                         printk(KERN_WARNING "%s: Error writing packet length; "
 266                                "rc = [%d]\n", __func__, rc);
 267                         goto out_unlock_msg_ctx;
 268                 }
 269         } else {
 270                 packet_length_size = 0;
 271                 msg_ctx->msg_size = 0;
 272         }
 273         total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size
 274                         + msg_ctx->msg_size);
 275         if (count < total_length) {
 276                 rc = 0;
 277                 printk(KERN_WARNING "%s: Only given user buffer of "
 278                        "size [%zd], but we need [%zd] to read the "
 279                        "pending message\n", __func__, count, total_length);
 280                 goto out_unlock_msg_ctx;
 281         }
 282         rc = -EFAULT;
 283         if (put_user(msg_ctx->type, buf))
 284                 goto out_unlock_msg_ctx;
 285         if (put_user(cpu_to_be32(msg_ctx->counter),
 286                      (__be32 __user *)(&buf[PKT_CTR_OFFSET])))
 287                 goto out_unlock_msg_ctx;
 288         i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
 289         if (msg_ctx->msg) {
 290                 if (copy_to_user(&buf[i], packet_length, packet_length_size))
 291                         goto out_unlock_msg_ctx;
 292                 i += packet_length_size;
 293                 if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
 294                         goto out_unlock_msg_ctx;
 295                 i += msg_ctx->msg_size;
 296         }
 297         rc = i;
 298         list_del(&msg_ctx->daemon_out_list);
 299         kfree(msg_ctx->msg);
 300         msg_ctx->msg = NULL;
 301         /* We do not expect a reply from the userspace daemon for any
 302          * message type other than ECRYPTFS_MSG_REQUEST */
 303         if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
 304                 ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 305 out_unlock_msg_ctx:
 306         mutex_unlock(&msg_ctx->mux);
 307 out_unlock_daemon:
 308         daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
 309         mutex_unlock(&daemon->mux);
 310         return rc;
 311 }
 312
 313 /**
 314  * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
 315  * @data: Bytes comprising struct ecryptfs_message
 316  * @data_size: sizeof(struct ecryptfs_message) + data len
 317  * @seq: Sequence number for miscdev response packet
 318  *
 319  * Returns zero on success; non-zero otherwise
 320  */
 321 static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
 322                                      size_t data_size, u32 seq)
 323 {
 324         struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
 325         int rc;
 326
 327         if ((sizeof(*msg) + msg->data_len) != data_size) {
 328                 printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
 329                        "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
 330                        (sizeof(*msg) + msg->data_len), data_size);
 331                 rc = -EINVAL;
 332                 goto out;
 333         }
 334         rc = ecryptfs_process_response(daemon, msg, seq);
 335         if (rc)
 336                 printk(KERN_ERR
 337                        "Error processing response message; rc = [%d]\n", rc);
 338 out:
 339         return rc;
 340 }
 341
 342 /**
 343  * ecryptfs_miscdev_write - handle write to daemon miscdev handle
 344  * @file: File for misc dev handle
 345  * @buf: Buffer containing user data
 346  * @count: Amount of data in @buf
 347  * @ppos: Pointer to offset in file (ignored)
 348  *
 349  * Returns the number of bytes read from @buf
 350  */
 351 static ssize_t
 352 ecryptfs_miscdev_write(struct file *file, const char __user *buf,
 353                        size_t count, loff_t *ppos)
 354 {
 355         __be32 counter_nbo;
 356         u32 seq;
 357         size_t packet_size, packet_size_length;
 358         char *data;
 359         unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
 360         ssize_t rc;
 361
 362         if (count == 0) {
 363                 return 0;
 364         } else if (count == MIN_NON_MSG_PKT_SIZE) {
 365                 /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
 366                 goto memdup;
 367         } else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
 368                 printk(KERN_WARNING "%s: Acceptable packet size range is "
 369                        "[%d-%zu], but amount of data written is [%zu].\n",
 370                        __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
 371                 return -EINVAL;
 372         }
 373
 374         if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
 375                            sizeof(packet_size_peek))) {
 376                 printk(KERN_WARNING "%s: Error while inspecting packet size\n",
 377                        __func__);
 378                 return -EFAULT;
 379         }
 380
 381         rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
 382                                           &packet_size_length);
 383         if (rc) {
 384                 printk(KERN_WARNING "%s: Error parsing packet length; "
 385                        "rc = [%zd]\n", __func__, rc);
 386                 return rc;
 387         }
 388
 389         if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
 390             != count) {
 391                 printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
 392                        packet_size);
 393                 return -EINVAL;
 394         }
 395
 396 memdup:
 397         data = memdup_user(buf, count);
 398         if (IS_ERR(data)) {
 399                 printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
 400                        __func__, PTR_ERR(data));
 401                 return PTR_ERR(data);
 402         }
 403         switch (data[PKT_TYPE_OFFSET]) {
 404         case ECRYPTFS_MSG_RESPONSE:
 405                 if (count < (MIN_MSG_PKT_SIZE
 406                              + sizeof(struct ecryptfs_message))) {
 407                         printk(KERN_WARNING "%s: Minimum acceptable packet "
 408                                "size is [%zd], but amount of data written is "
 409                                "only [%zd]. Discarding response packet.\n",
 410                                __func__,
 411                                (MIN_MSG_PKT_SIZE
 412                                 + sizeof(struct ecryptfs_message)), count);
 413                         rc = -EINVAL;
 414                         goto out_free;
 415                 }
 416                 memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
 417                 seq = be32_to_cpu(counter_nbo);
 418                 rc = ecryptfs_miscdev_response(file->private_data,
 419                                 &data[PKT_LEN_OFFSET + packet_size_length],
 420                                 packet_size, seq);
 421                 if (rc) {
 422                         printk(KERN_WARNING "%s: Failed to deliver miscdev "
 423                                "response to requesting operation; rc = [%zd]\n",
 424                                __func__, rc);
 425                         goto out_free;
 426                 }
 427                 break;
 428         case ECRYPTFS_MSG_HELO:
 429         case ECRYPTFS_MSG_QUIT:
 430                 break;
 431         default:
 432                 ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
 433                                 "message of unrecognized type [%d]\n",
 434                                 data[0]);
 435                 rc = -EINVAL;
 436                 goto out_free;
 437         }
 438         rc = count;
 439 out_free:
 440         kfree(data);
 441         return rc;
 442 }
 443
 444
 445 static const struct file_operations ecryptfs_miscdev_fops = {
 446         .owner   = THIS_MODULE,
 447         .open    = ecryptfs_miscdev_open,
 448         .poll    = ecryptfs_miscdev_poll,
 449         .read    = ecryptfs_miscdev_read,
 450         .write   = ecryptfs_miscdev_write,
 451         .release = ecryptfs_miscdev_release,
 452         .llseek  = noop_llseek,
 453 };
 454
 455 static struct miscdevice ecryptfs_miscdev = {
 456         .minor = MISC_DYNAMIC_MINOR,
 457         .name  = "ecryptfs",
 458         .fops  = &ecryptfs_miscdev_fops
 459 };
 460
 461 /**
 462  * ecryptfs_init_ecryptfs_miscdev
 463  *
 464  * Messages sent to the userspace daemon from the kernel are placed on
 465  * a queue associated with the daemon. The next read against the
 466  * miscdev handle by that daemon will return the oldest message placed
 467  * on the message queue for the daemon.
 468  *
 469  * Returns zero on success; non-zero otherwise
 470  */
 471 int __init ecryptfs_init_ecryptfs_miscdev(void)
 472 {
 473         int rc;
 474
 475         atomic_set(&ecryptfs_num_miscdev_opens, 0);
 476         rc = misc_register(&ecryptfs_miscdev);
 477         if (rc)
 478                 printk(KERN_ERR "%s: Failed to register miscellaneous device "
 479                        "for communications with userspace daemons; rc = [%d]\n",
 480                        __func__, rc);
 481         return rc;
 482 }
 483
 484 /**
 485  * ecryptfs_destroy_ecryptfs_miscdev
 486  *
 487  * All of the daemons must be exorcised prior to calling this
 488  * function.
 489  */
 490 void ecryptfs_destroy_ecryptfs_miscdev(void)
 491 {
 492         BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
 493         misc_deregister(&ecryptfs_miscdev);
 494 }