linux/fs/ecryptfs/messaging.c
<<
>>
Prefs
   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)from_kuid(&init_user_ns, 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 (uid_eq((*daemon)->file->f_cred->euid, current_euid())) {
 125                        rc = 0;
 126                        goto out;
 127                }
 128        }
 129        rc = -EINVAL;
 130out:
 131        return rc;
 132}
 133
 134/**
 135 * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
 136 * @daemon: Pointer to set to newly allocated daemon struct
 137 * @file: File used when opening /dev/ecryptfs
 138 *
 139 * Must be called ceremoniously while in possession of
 140 * ecryptfs_sacred_daemon_hash_mux
 141 *
 142 * Returns zero on success; non-zero otherwise
 143 */
 144int
 145ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
 146{
 147        int rc = 0;
 148
 149        (*daemon) = kzalloc(sizeof(**daemon), GFP_KERNEL);
 150        if (!(*daemon)) {
 151                rc = -ENOMEM;
 152                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
 153                       "GFP_KERNEL memory\n", __func__, sizeof(**daemon));
 154                goto out;
 155        }
 156        (*daemon)->file = file;
 157        mutex_init(&(*daemon)->mux);
 158        INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
 159        init_waitqueue_head(&(*daemon)->wait);
 160        (*daemon)->num_queued_msg_ctx = 0;
 161        hlist_add_head(&(*daemon)->euid_chain,
 162                       &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
 163out:
 164        return rc;
 165}
 166
 167/**
 168 * ecryptfs_exorcise_daemon - Destroy the daemon struct
 169 *
 170 * Must be called ceremoniously while in possession of
 171 * ecryptfs_daemon_hash_mux and the daemon's own mux.
 172 */
 173int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
 174{
 175        struct ecryptfs_msg_ctx *msg_ctx, *msg_ctx_tmp;
 176        int rc = 0;
 177
 178        mutex_lock(&daemon->mux);
 179        if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
 180            || (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
 181                rc = -EBUSY;
 182                mutex_unlock(&daemon->mux);
 183                goto out;
 184        }
 185        list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
 186                                 &daemon->msg_ctx_out_queue, daemon_out_list) {
 187                list_del(&msg_ctx->daemon_out_list);
 188                daemon->num_queued_msg_ctx--;
 189                printk(KERN_WARNING "%s: Warning: dropping message that is in "
 190                       "the out queue of a dying daemon\n", __func__);
 191                ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 192        }
 193        hlist_del(&daemon->euid_chain);
 194        mutex_unlock(&daemon->mux);
 195        kzfree(daemon);
 196out:
 197        return rc;
 198}
 199
 200/**
 201 * ecryptfs_process_reponse
 202 * @msg: The ecryptfs message received; the caller should sanity check
 203 *       msg->data_len and free the memory
 204 * @seq: The sequence number of the message; must match the sequence
 205 *       number for the existing message context waiting for this
 206 *       response
 207 *
 208 * Processes a response message after sending an operation request to
 209 * userspace. Some other process is awaiting this response. Before
 210 * sending out its first communications, the other process allocated a
 211 * msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
 212 * response message contains this index so that we can copy over the
 213 * response message into the msg_ctx that the process holds a
 214 * reference to. The other process is going to wake up, check to see
 215 * that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
 216 * proceed to read off and process the response message. Returns zero
 217 * upon delivery to desired context element; non-zero upon delivery
 218 * failure or error.
 219 *
 220 * Returns zero on success; non-zero otherwise
 221 */
 222int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
 223                              struct ecryptfs_message *msg, u32 seq)
 224{
 225        struct ecryptfs_msg_ctx *msg_ctx;
 226        size_t msg_size;
 227        int rc;
 228
 229        if (msg->index >= ecryptfs_message_buf_len) {
 230                rc = -EINVAL;
 231                printk(KERN_ERR "%s: Attempt to reference "
 232                       "context buffer at index [%d]; maximum "
 233                       "allowable is [%d]\n", __func__, msg->index,
 234                       (ecryptfs_message_buf_len - 1));
 235                goto out;
 236        }
 237        msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
 238        mutex_lock(&msg_ctx->mux);
 239        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
 240                rc = -EINVAL;
 241                printk(KERN_WARNING "%s: Desired context element is not "
 242                       "pending a response\n", __func__);
 243                goto unlock;
 244        } else if (msg_ctx->counter != seq) {
 245                rc = -EINVAL;
 246                printk(KERN_WARNING "%s: Invalid message sequence; "
 247                       "expected [%d]; received [%d]\n", __func__,
 248                       msg_ctx->counter, seq);
 249                goto unlock;
 250        }
 251        msg_size = (sizeof(*msg) + msg->data_len);
 252        msg_ctx->msg = kmalloc(msg_size, GFP_KERNEL);
 253        if (!msg_ctx->msg) {
 254                rc = -ENOMEM;
 255                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
 256                       "GFP_KERNEL memory\n", __func__, msg_size);
 257                goto unlock;
 258        }
 259        memcpy(msg_ctx->msg, msg, msg_size);
 260        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
 261        wake_up_process(msg_ctx->task);
 262        rc = 0;
 263unlock:
 264        mutex_unlock(&msg_ctx->mux);
 265out:
 266        return rc;
 267}
 268
 269/**
 270 * ecryptfs_send_message_locked
 271 * @data: The data to send
 272 * @data_len: The length of data
 273 * @msg_ctx: The message context allocated for the send
 274 *
 275 * Must be called with ecryptfs_daemon_hash_mux held.
 276 *
 277 * Returns zero on success; non-zero otherwise
 278 */
 279static int
 280ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
 281                             struct ecryptfs_msg_ctx **msg_ctx)
 282{
 283        struct ecryptfs_daemon *daemon;
 284        int rc;
 285
 286        rc = ecryptfs_find_daemon_by_euid(&daemon);
 287        if (rc || !daemon) {
 288                rc = -ENOTCONN;
 289                goto out;
 290        }
 291        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 292        rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
 293        if (rc) {
 294                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 295                printk(KERN_WARNING "%s: Could not claim a free "
 296                       "context element\n", __func__);
 297                goto out;
 298        }
 299        ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
 300        mutex_unlock(&(*msg_ctx)->mux);
 301        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 302        rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
 303                                   daemon);
 304        if (rc)
 305                printk(KERN_ERR "%s: Error attempting to send message to "
 306                       "userspace daemon; rc = [%d]\n", __func__, rc);
 307out:
 308        return rc;
 309}
 310
 311/**
 312 * ecryptfs_send_message
 313 * @data: The data to send
 314 * @data_len: The length of data
 315 * @msg_ctx: The message context allocated for the send
 316 *
 317 * Grabs ecryptfs_daemon_hash_mux.
 318 *
 319 * Returns zero on success; non-zero otherwise
 320 */
 321int ecryptfs_send_message(char *data, int data_len,
 322                          struct ecryptfs_msg_ctx **msg_ctx)
 323{
 324        int rc;
 325
 326        mutex_lock(&ecryptfs_daemon_hash_mux);
 327        rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
 328                                          msg_ctx);
 329        mutex_unlock(&ecryptfs_daemon_hash_mux);
 330        return rc;
 331}
 332
 333/**
 334 * ecryptfs_wait_for_response
 335 * @msg_ctx: The context that was assigned when sending a message
 336 * @msg: The incoming message from userspace; not set if rc != 0
 337 *
 338 * Sleeps until awaken by ecryptfs_receive_message or until the amount
 339 * of time exceeds ecryptfs_message_wait_timeout.  If zero is
 340 * returned, msg will point to a valid message from userspace; a
 341 * non-zero value is returned upon failure to receive a message or an
 342 * error occurs. Callee must free @msg on success.
 343 */
 344int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
 345                               struct ecryptfs_message **msg)
 346{
 347        signed long timeout = ecryptfs_message_wait_timeout * HZ;
 348        int rc = 0;
 349
 350sleep:
 351        timeout = schedule_timeout_interruptible(timeout);
 352        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 353        mutex_lock(&msg_ctx->mux);
 354        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
 355                if (timeout) {
 356                        mutex_unlock(&msg_ctx->mux);
 357                        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 358                        goto sleep;
 359                }
 360                rc = -ENOMSG;
 361        } else {
 362                *msg = msg_ctx->msg;
 363                msg_ctx->msg = NULL;
 364        }
 365        ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 366        mutex_unlock(&msg_ctx->mux);
 367        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 368        return rc;
 369}
 370
 371int __init ecryptfs_init_messaging(void)
 372{
 373        int i;
 374        int rc = 0;
 375
 376        if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
 377                ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
 378                printk(KERN_WARNING "%s: Specified number of users is "
 379                       "too large, defaulting to [%d] users\n", __func__,
 380                       ecryptfs_number_of_users);
 381        }
 382        mutex_init(&ecryptfs_daemon_hash_mux);
 383        mutex_lock(&ecryptfs_daemon_hash_mux);
 384        ecryptfs_hash_bits = 1;
 385        while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
 386                ecryptfs_hash_bits++;
 387        ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
 388                                        * (1 << ecryptfs_hash_bits)),
 389                                       GFP_KERNEL);
 390        if (!ecryptfs_daemon_hash) {
 391                rc = -ENOMEM;
 392                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
 393                mutex_unlock(&ecryptfs_daemon_hash_mux);
 394                goto out;
 395        }
 396        for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
 397                INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
 398        mutex_unlock(&ecryptfs_daemon_hash_mux);
 399        ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
 400                                        * ecryptfs_message_buf_len),
 401                                       GFP_KERNEL);
 402        if (!ecryptfs_msg_ctx_arr) {
 403                rc = -ENOMEM;
 404                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
 405                goto out;
 406        }
 407        mutex_init(&ecryptfs_msg_ctx_lists_mux);
 408        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 409        ecryptfs_msg_counter = 0;
 410        for (i = 0; i < ecryptfs_message_buf_len; i++) {
 411                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
 412                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
 413                mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
 414                mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 415                ecryptfs_msg_ctx_arr[i].index = i;
 416                ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
 417                ecryptfs_msg_ctx_arr[i].counter = 0;
 418                ecryptfs_msg_ctx_arr[i].task = NULL;
 419                ecryptfs_msg_ctx_arr[i].msg = NULL;
 420                list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
 421                              &ecryptfs_msg_ctx_free_list);
 422                mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 423        }
 424        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 425        rc = ecryptfs_init_ecryptfs_miscdev();
 426        if (rc)
 427                ecryptfs_release_messaging();
 428out:
 429        return rc;
 430}
 431
 432void ecryptfs_release_messaging(void)
 433{
 434        if (ecryptfs_msg_ctx_arr) {
 435                int i;
 436
 437                mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 438                for (i = 0; i < ecryptfs_message_buf_len; i++) {
 439                        mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 440                        if (ecryptfs_msg_ctx_arr[i].msg)
 441                                kfree(ecryptfs_msg_ctx_arr[i].msg);
 442                        mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 443                }
 444                kfree(ecryptfs_msg_ctx_arr);
 445                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 446        }
 447        if (ecryptfs_daemon_hash) {
 448                struct hlist_node *elem;
 449                struct ecryptfs_daemon *daemon;
 450                int i;
 451
 452                mutex_lock(&ecryptfs_daemon_hash_mux);
 453                for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
 454                        int rc;
 455
 456                        hlist_for_each_entry(daemon, elem,
 457                                             &ecryptfs_daemon_hash[i],
 458                                             euid_chain) {
 459                                rc = ecryptfs_exorcise_daemon(daemon);
 460                                if (rc)
 461                                        printk(KERN_ERR "%s: Error whilst "
 462                                               "attempting to destroy daemon; "
 463                                               "rc = [%d]. Dazed and confused, "
 464                                               "but trying to continue.\n",
 465                                               __func__, rc);
 466                        }
 467                }
 468                kfree(ecryptfs_daemon_hash);
 469                mutex_unlock(&ecryptfs_daemon_hash_mux);
 470        }
 471        ecryptfs_destroy_ecryptfs_miscdev();
 472        return;
 473}
 474
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.