linux/fs/ecryptfs/messaging.c
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   1/**
   2 * eCryptfs: Linux filesystem encryption layer
   3 *
   4 * Copyright (C) 2004-2008 International Business Machines Corp.
   5 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   6 *              Tyler Hicks <tyhicks@ou.edu>
   7 *
   8 * This program is free software; you can redistribute it and/or
   9 * modify it under the terms of the GNU General Public License version
  10 * 2 as published by the Free Software Foundation.
  11 *
  12 * This program is distributed in the hope that it will be useful, but
  13 * WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 * General Public License for more details.
  16 *
  17 * You should have received a copy of the GNU General Public License
  18 * along with this program; if not, write to the Free Software
  19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20 * 02111-1307, USA.
  21 */
  22#include <linux/sched.h>
  23#include <linux/slab.h>
  24#include <linux/user_namespace.h>
  25#include <linux/nsproxy.h>
  26#include "ecryptfs_kernel.h"
  27
  28static LIST_HEAD(ecryptfs_msg_ctx_free_list);
  29static LIST_HEAD(ecryptfs_msg_ctx_alloc_list);
  30static struct mutex ecryptfs_msg_ctx_lists_mux;
  31
  32static struct hlist_head *ecryptfs_daemon_hash;
  33struct mutex ecryptfs_daemon_hash_mux;
  34static int ecryptfs_hash_bits;
  35#define ecryptfs_current_euid_hash(uid) \
  36                hash_long((unsigned long)current_euid(), ecryptfs_hash_bits)
  37
  38static u32 ecryptfs_msg_counter;
  39static struct ecryptfs_msg_ctx *ecryptfs_msg_ctx_arr;
  40
  41/**
  42 * ecryptfs_acquire_free_msg_ctx
  43 * @msg_ctx: The context that was acquired from the free list
  44 *
  45 * Acquires a context element from the free list and locks the mutex
  46 * on the context.  Sets the msg_ctx task to current.  Returns zero on
  47 * success; non-zero on error or upon failure to acquire a free
  48 * context element.  Must be called with ecryptfs_msg_ctx_lists_mux
  49 * held.
  50 */
  51static int ecryptfs_acquire_free_msg_ctx(struct ecryptfs_msg_ctx **msg_ctx)
  52{
  53        struct list_head *p;
  54        int rc;
  55
  56        if (list_empty(&ecryptfs_msg_ctx_free_list)) {
  57                printk(KERN_WARNING "%s: The eCryptfs free "
  58                       "context list is empty.  It may be helpful to "
  59                       "specify the ecryptfs_message_buf_len "
  60                       "parameter to be greater than the current "
  61                       "value of [%d]\n", __func__, ecryptfs_message_buf_len);
  62                rc = -ENOMEM;
  63                goto out;
  64        }
  65        list_for_each(p, &ecryptfs_msg_ctx_free_list) {
  66                *msg_ctx = list_entry(p, struct ecryptfs_msg_ctx, node);
  67                if (mutex_trylock(&(*msg_ctx)->mux)) {
  68                        (*msg_ctx)->task = current;
  69                        rc = 0;
  70                        goto out;
  71                }
  72        }
  73        rc = -ENOMEM;
  74out:
  75        return rc;
  76}
  77
  78/**
  79 * ecryptfs_msg_ctx_free_to_alloc
  80 * @msg_ctx: The context to move from the free list to the alloc list
  81 *
  82 * Must be called with ecryptfs_msg_ctx_lists_mux held.
  83 */
  84static void ecryptfs_msg_ctx_free_to_alloc(struct ecryptfs_msg_ctx *msg_ctx)
  85{
  86        list_move(&msg_ctx->node, &ecryptfs_msg_ctx_alloc_list);
  87        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_PENDING;
  88        msg_ctx->counter = ++ecryptfs_msg_counter;
  89}
  90
  91/**
  92 * ecryptfs_msg_ctx_alloc_to_free
  93 * @msg_ctx: The context to move from the alloc list to the free list
  94 *
  95 * Must be called with ecryptfs_msg_ctx_lists_mux held.
  96 */
  97void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx)
  98{
  99        list_move(&(msg_ctx->node), &ecryptfs_msg_ctx_free_list);
 100        if (msg_ctx->msg)
 101                kfree(msg_ctx->msg);
 102        msg_ctx->msg = NULL;
 103        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_FREE;
 104}
 105
 106/**
 107 * ecryptfs_find_daemon_by_euid
 108 * @daemon: If return value is zero, points to the desired daemon pointer
 109 *
 110 * Must be called with ecryptfs_daemon_hash_mux held.
 111 *
 112 * Search the hash list for the current effective user id.
 113 *
 114 * Returns zero if the user id exists in the list; non-zero otherwise.
 115 */
 116int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
 117{
 118        struct hlist_node *elem;
 119        int rc;
 120
 121        hlist_for_each_entry(*daemon, elem,
 122                            &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()],
 123                            euid_chain) {
 124                if ((*daemon)->file->f_cred->euid == current_euid() &&
 125                    (*daemon)->file->f_cred->user_ns == current_user_ns()) {
 126                        rc = 0;
 127                        goto out;
 128                }
 129        }
 130        rc = -EINVAL;
 131out:
 132        return rc;
 133}
 134
 135/**
 136 * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
 137 * @daemon: Pointer to set to newly allocated daemon struct
 138 * @file: File used when opening /dev/ecryptfs
 139 *
 140 * Must be called ceremoniously while in possession of
 141 * ecryptfs_sacred_daemon_hash_mux
 142 *
 143 * Returns zero on success; non-zero otherwise
 144 */
 145int
 146ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
 147{
 148        int rc = 0;
 149
 150        (*daemon) = kzalloc(sizeof(**daemon), GFP_KERNEL);
 151        if (!(*daemon)) {
 152                rc = -ENOMEM;
 153                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
 154                       "GFP_KERNEL memory\n", __func__, sizeof(**daemon));
 155                goto out;
 156        }
 157        (*daemon)->file = file;
 158        mutex_init(&(*daemon)->mux);
 159        INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
 160        init_waitqueue_head(&(*daemon)->wait);
 161        (*daemon)->num_queued_msg_ctx = 0;
 162        hlist_add_head(&(*daemon)->euid_chain,
 163                       &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
 164out:
 165        return rc;
 166}
 167
 168/**
 169 * ecryptfs_exorcise_daemon - Destroy the daemon struct
 170 *
 171 * Must be called ceremoniously while in possession of
 172 * ecryptfs_daemon_hash_mux and the daemon's own mux.
 173 */
 174int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
 175{
 176        struct ecryptfs_msg_ctx *msg_ctx, *msg_ctx_tmp;
 177        int rc = 0;
 178
 179        mutex_lock(&daemon->mux);
 180        if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
 181            || (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
 182                rc = -EBUSY;
 183                mutex_unlock(&daemon->mux);
 184                goto out;
 185        }
 186        list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
 187                                 &daemon->msg_ctx_out_queue, daemon_out_list) {
 188                list_del(&msg_ctx->daemon_out_list);
 189                daemon->num_queued_msg_ctx--;
 190                printk(KERN_WARNING "%s: Warning: dropping message that is in "
 191                       "the out queue of a dying daemon\n", __func__);
 192                ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 193        }
 194        hlist_del(&daemon->euid_chain);
 195        mutex_unlock(&daemon->mux);
 196        kzfree(daemon);
 197out:
 198        return rc;
 199}
 200
 201/**
 202 * ecryptfs_process_reponse
 203 * @msg: The ecryptfs message received; the caller should sanity check
 204 *       msg->data_len and free the memory
 205 * @seq: The sequence number of the message; must match the sequence
 206 *       number for the existing message context waiting for this
 207 *       response
 208 *
 209 * Processes a response message after sending an operation request to
 210 * userspace. Some other process is awaiting this response. Before
 211 * sending out its first communications, the other process allocated a
 212 * msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
 213 * response message contains this index so that we can copy over the
 214 * response message into the msg_ctx that the process holds a
 215 * reference to. The other process is going to wake up, check to see
 216 * that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
 217 * proceed to read off and process the response message. Returns zero
 218 * upon delivery to desired context element; non-zero upon delivery
 219 * failure or error.
 220 *
 221 * Returns zero on success; non-zero otherwise
 222 */
 223int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
 224                              struct ecryptfs_message *msg, u32 seq)
 225{
 226        struct ecryptfs_msg_ctx *msg_ctx;
 227        size_t msg_size;
 228        int rc;
 229
 230        if (msg->index >= ecryptfs_message_buf_len) {
 231                rc = -EINVAL;
 232                printk(KERN_ERR "%s: Attempt to reference "
 233                       "context buffer at index [%d]; maximum "
 234                       "allowable is [%d]\n", __func__, msg->index,
 235                       (ecryptfs_message_buf_len - 1));
 236                goto out;
 237        }
 238        msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
 239        mutex_lock(&msg_ctx->mux);
 240        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
 241                rc = -EINVAL;
 242                printk(KERN_WARNING "%s: Desired context element is not "
 243                       "pending a response\n", __func__);
 244                goto unlock;
 245        } else if (msg_ctx->counter != seq) {
 246                rc = -EINVAL;
 247                printk(KERN_WARNING "%s: Invalid message sequence; "
 248                       "expected [%d]; received [%d]\n", __func__,
 249                       msg_ctx->counter, seq);
 250                goto unlock;
 251        }
 252        msg_size = (sizeof(*msg) + msg->data_len);
 253        msg_ctx->msg = kmalloc(msg_size, GFP_KERNEL);
 254        if (!msg_ctx->msg) {
 255                rc = -ENOMEM;
 256                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
 257                       "GFP_KERNEL memory\n", __func__, msg_size);
 258                goto unlock;
 259        }
 260        memcpy(msg_ctx->msg, msg, msg_size);
 261        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
 262        wake_up_process(msg_ctx->task);
 263        rc = 0;
 264unlock:
 265        mutex_unlock(&msg_ctx->mux);
 266out:
 267        return rc;
 268}
 269
 270/**
 271 * ecryptfs_send_message_locked
 272 * @data: The data to send
 273 * @data_len: The length of data
 274 * @msg_ctx: The message context allocated for the send
 275 *
 276 * Must be called with ecryptfs_daemon_hash_mux held.
 277 *
 278 * Returns zero on success; non-zero otherwise
 279 */
 280static int
 281ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
 282                             struct ecryptfs_msg_ctx **msg_ctx)
 283{
 284        struct ecryptfs_daemon *daemon;
 285        int rc;
 286
 287        rc = ecryptfs_find_daemon_by_euid(&daemon);
 288        if (rc || !daemon) {
 289                rc = -ENOTCONN;
 290                goto out;
 291        }
 292        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 293        rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
 294        if (rc) {
 295                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 296                printk(KERN_WARNING "%s: Could not claim a free "
 297                       "context element\n", __func__);
 298                goto out;
 299        }
 300        ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
 301        mutex_unlock(&(*msg_ctx)->mux);
 302        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 303        rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
 304                                   daemon);
 305        if (rc)
 306                printk(KERN_ERR "%s: Error attempting to send message to "
 307                       "userspace daemon; rc = [%d]\n", __func__, rc);
 308out:
 309        return rc;
 310}
 311
 312/**
 313 * ecryptfs_send_message
 314 * @data: The data to send
 315 * @data_len: The length of data
 316 * @msg_ctx: The message context allocated for the send
 317 *
 318 * Grabs ecryptfs_daemon_hash_mux.
 319 *
 320 * Returns zero on success; non-zero otherwise
 321 */
 322int ecryptfs_send_message(char *data, int data_len,
 323                          struct ecryptfs_msg_ctx **msg_ctx)
 324{
 325        int rc;
 326
 327        mutex_lock(&ecryptfs_daemon_hash_mux);
 328        rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
 329                                          msg_ctx);
 330        mutex_unlock(&ecryptfs_daemon_hash_mux);
 331        return rc;
 332}
 333
 334/**
 335 * ecryptfs_wait_for_response
 336 * @msg_ctx: The context that was assigned when sending a message
 337 * @msg: The incoming message from userspace; not set if rc != 0
 338 *
 339 * Sleeps until awaken by ecryptfs_receive_message or until the amount
 340 * of time exceeds ecryptfs_message_wait_timeout.  If zero is
 341 * returned, msg will point to a valid message from userspace; a
 342 * non-zero value is returned upon failure to receive a message or an
 343 * error occurs. Callee must free @msg on success.
 344 */
 345int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
 346                               struct ecryptfs_message **msg)
 347{
 348        signed long timeout = ecryptfs_message_wait_timeout * HZ;
 349        int rc = 0;
 350
 351sleep:
 352        timeout = schedule_timeout_interruptible(timeout);
 353        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 354        mutex_lock(&msg_ctx->mux);
 355        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
 356                if (timeout) {
 357                        mutex_unlock(&msg_ctx->mux);
 358                        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 359                        goto sleep;
 360                }
 361                rc = -ENOMSG;
 362        } else {
 363                *msg = msg_ctx->msg;
 364                msg_ctx->msg = NULL;
 365        }
 366        ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 367        mutex_unlock(&msg_ctx->mux);
 368        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 369        return rc;
 370}
 371
 372int __init ecryptfs_init_messaging(void)
 373{
 374        int i;
 375        int rc = 0;
 376
 377        if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
 378                ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
 379                printk(KERN_WARNING "%s: Specified number of users is "
 380                       "too large, defaulting to [%d] users\n", __func__,
 381                       ecryptfs_number_of_users);
 382        }
 383        mutex_init(&ecryptfs_daemon_hash_mux);
 384        mutex_lock(&ecryptfs_daemon_hash_mux);
 385        ecryptfs_hash_bits = 1;
 386        while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
 387                ecryptfs_hash_bits++;
 388        ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
 389                                        * (1 << ecryptfs_hash_bits)),
 390                                       GFP_KERNEL);
 391        if (!ecryptfs_daemon_hash) {
 392                rc = -ENOMEM;
 393                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
 394                mutex_unlock(&ecryptfs_daemon_hash_mux);
 395                goto out;
 396        }
 397        for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
 398                INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
 399        mutex_unlock(&ecryptfs_daemon_hash_mux);
 400        ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
 401                                        * ecryptfs_message_buf_len),
 402                                       GFP_KERNEL);
 403        if (!ecryptfs_msg_ctx_arr) {
 404                rc = -ENOMEM;
 405                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
 406                goto out;
 407        }
 408        mutex_init(&ecryptfs_msg_ctx_lists_mux);
 409        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 410        ecryptfs_msg_counter = 0;
 411        for (i = 0; i < ecryptfs_message_buf_len; i++) {
 412                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
 413                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
 414                mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
 415                mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 416                ecryptfs_msg_ctx_arr[i].index = i;
 417                ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
 418                ecryptfs_msg_ctx_arr[i].counter = 0;
 419                ecryptfs_msg_ctx_arr[i].task = NULL;
 420                ecryptfs_msg_ctx_arr[i].msg = NULL;
 421                list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
 422                              &ecryptfs_msg_ctx_free_list);
 423                mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 424        }
 425        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 426        rc = ecryptfs_init_ecryptfs_miscdev();
 427        if (rc)
 428                ecryptfs_release_messaging();
 429out:
 430        return rc;
 431}
 432
 433void ecryptfs_release_messaging(void)
 434{
 435        if (ecryptfs_msg_ctx_arr) {
 436                int i;
 437
 438                mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 439                for (i = 0; i < ecryptfs_message_buf_len; i++) {
 440                        mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 441                        if (ecryptfs_msg_ctx_arr[i].msg)
 442                                kfree(ecryptfs_msg_ctx_arr[i].msg);
 443                        mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 444                }
 445                kfree(ecryptfs_msg_ctx_arr);
 446                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 447        }
 448        if (ecryptfs_daemon_hash) {
 449                struct hlist_node *elem;
 450                struct ecryptfs_daemon *daemon;
 451                int i;
 452
 453                mutex_lock(&ecryptfs_daemon_hash_mux);
 454                for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
 455                        int rc;
 456
 457                        hlist_for_each_entry(daemon, elem,
 458                                             &ecryptfs_daemon_hash[i],
 459                                             euid_chain) {
 460                                rc = ecryptfs_exorcise_daemon(daemon);
 461                                if (rc)
 462                                        printk(KERN_ERR "%s: Error whilst "
 463                                               "attempting to destroy daemon; "
 464                                               "rc = [%d]. Dazed and confused, "
 465                                               "but trying to continue.\n",
 466                                               __func__, rc);
 467                        }
 468                }
 469                kfree(ecryptfs_daemon_hash);
 470                mutex_unlock(&ecryptfs_daemon_hash_mux);
 471        }
 472        ecryptfs_destroy_ecryptfs_miscdev();
 473        return;
 474}
 475
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