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