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)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        kfree(msg_ctx->msg);
 101        msg_ctx->msg = NULL;
 102        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_FREE;
 103}
 104
 105/**
 106 * ecryptfs_find_daemon_by_euid
 107 * @daemon: If return value is zero, points to the desired daemon pointer
 108 *
 109 * Must be called with ecryptfs_daemon_hash_mux held.
 110 *
 111 * Search the hash list for the current effective user id.
 112 *
 113 * Returns zero if the user id exists in the list; non-zero otherwise.
 114 */
 115int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
 116{
 117        int rc;
 118
 119        hlist_for_each_entry(*daemon,
 120                            &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()],
 121                            euid_chain) {
 122                if (uid_eq((*daemon)->file->f_cred->euid, current_euid())) {
 123                        rc = 0;
 124                        goto out;
 125                }
 126        }
 127        rc = -EINVAL;
 128out:
 129        return rc;
 130}
 131
 132/**
 133 * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
 134 * @daemon: Pointer to set to newly allocated daemon struct
 135 * @file: File used when opening /dev/ecryptfs
 136 *
 137 * Must be called ceremoniously while in possession of
 138 * ecryptfs_sacred_daemon_hash_mux
 139 *
 140 * Returns zero on success; non-zero otherwise
 141 */
 142int
 143ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
 144{
 145        int rc = 0;
 146
 147        (*daemon) = kzalloc(sizeof(**daemon), GFP_KERNEL);
 148        if (!(*daemon)) {
 149                rc = -ENOMEM;
 150                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
 151                       "GFP_KERNEL memory\n", __func__, sizeof(**daemon));
 152                goto out;
 153        }
 154        (*daemon)->file = file;
 155        mutex_init(&(*daemon)->mux);
 156        INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
 157        init_waitqueue_head(&(*daemon)->wait);
 158        (*daemon)->num_queued_msg_ctx = 0;
 159        hlist_add_head(&(*daemon)->euid_chain,
 160                       &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
 161out:
 162        return rc;
 163}
 164
 165/**
 166 * ecryptfs_exorcise_daemon - Destroy the daemon struct
 167 *
 168 * Must be called ceremoniously while in possession of
 169 * ecryptfs_daemon_hash_mux and the daemon's own mux.
 170 */
 171int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
 172{
 173        struct ecryptfs_msg_ctx *msg_ctx, *msg_ctx_tmp;
 174        int rc = 0;
 175
 176        mutex_lock(&daemon->mux);
 177        if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
 178            || (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
 179                rc = -EBUSY;
 180                mutex_unlock(&daemon->mux);
 181                goto out;
 182        }
 183        list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
 184                                 &daemon->msg_ctx_out_queue, daemon_out_list) {
 185                list_del(&msg_ctx->daemon_out_list);
 186                daemon->num_queued_msg_ctx--;
 187                printk(KERN_WARNING "%s: Warning: dropping message that is in "
 188                       "the out queue of a dying daemon\n", __func__);
 189                ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 190        }
 191        hlist_del(&daemon->euid_chain);
 192        mutex_unlock(&daemon->mux);
 193        kzfree(daemon);
 194out:
 195        return rc;
 196}
 197
 198/**
 199 * ecryptfs_process_reponse
 200 * @msg: The ecryptfs message received; the caller should sanity check
 201 *       msg->data_len and free the memory
 202 * @seq: The sequence number of the message; must match the sequence
 203 *       number for the existing message context waiting for this
 204 *       response
 205 *
 206 * Processes a response message after sending an operation request to
 207 * userspace. Some other process is awaiting this response. Before
 208 * sending out its first communications, the other process allocated a
 209 * msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
 210 * response message contains this index so that we can copy over the
 211 * response message into the msg_ctx that the process holds a
 212 * reference to. The other process is going to wake up, check to see
 213 * that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
 214 * proceed to read off and process the response message. Returns zero
 215 * upon delivery to desired context element; non-zero upon delivery
 216 * failure or error.
 217 *
 218 * Returns zero on success; non-zero otherwise
 219 */
 220int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
 221                              struct ecryptfs_message *msg, u32 seq)
 222{
 223        struct ecryptfs_msg_ctx *msg_ctx;
 224        size_t msg_size;
 225        int rc;
 226
 227        if (msg->index >= ecryptfs_message_buf_len) {
 228                rc = -EINVAL;
 229                printk(KERN_ERR "%s: Attempt to reference "
 230                       "context buffer at index [%d]; maximum "
 231                       "allowable is [%d]\n", __func__, msg->index,
 232                       (ecryptfs_message_buf_len - 1));
 233                goto out;
 234        }
 235        msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
 236        mutex_lock(&msg_ctx->mux);
 237        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
 238                rc = -EINVAL;
 239                printk(KERN_WARNING "%s: Desired context element is not "
 240                       "pending a response\n", __func__);
 241                goto unlock;
 242        } else if (msg_ctx->counter != seq) {
 243                rc = -EINVAL;
 244                printk(KERN_WARNING "%s: Invalid message sequence; "
 245                       "expected [%d]; received [%d]\n", __func__,
 246                       msg_ctx->counter, seq);
 247                goto unlock;
 248        }
 249        msg_size = (sizeof(*msg) + msg->data_len);
 250        msg_ctx->msg = kmemdup(msg, msg_size, GFP_KERNEL);
 251        if (!msg_ctx->msg) {
 252                rc = -ENOMEM;
 253                printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
 254                       "GFP_KERNEL memory\n", __func__, msg_size);
 255                goto unlock;
 256        }
 257        msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
 258        wake_up_process(msg_ctx->task);
 259        rc = 0;
 260unlock:
 261        mutex_unlock(&msg_ctx->mux);
 262out:
 263        return rc;
 264}
 265
 266/**
 267 * ecryptfs_send_message_locked
 268 * @data: The data to send
 269 * @data_len: The length of data
 270 * @msg_ctx: The message context allocated for the send
 271 *
 272 * Must be called with ecryptfs_daemon_hash_mux held.
 273 *
 274 * Returns zero on success; non-zero otherwise
 275 */
 276static int
 277ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
 278                             struct ecryptfs_msg_ctx **msg_ctx)
 279{
 280        struct ecryptfs_daemon *daemon;
 281        int rc;
 282
 283        rc = ecryptfs_find_daemon_by_euid(&daemon);
 284        if (rc) {
 285                rc = -ENOTCONN;
 286                goto out;
 287        }
 288        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 289        rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
 290        if (rc) {
 291                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 292                printk(KERN_WARNING "%s: Could not claim a free "
 293                       "context element\n", __func__);
 294                goto out;
 295        }
 296        ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
 297        mutex_unlock(&(*msg_ctx)->mux);
 298        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 299        rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
 300                                   daemon);
 301        if (rc)
 302                printk(KERN_ERR "%s: Error attempting to send message to "
 303                       "userspace daemon; rc = [%d]\n", __func__, rc);
 304out:
 305        return rc;
 306}
 307
 308/**
 309 * ecryptfs_send_message
 310 * @data: The data to send
 311 * @data_len: The length of data
 312 * @msg_ctx: The message context allocated for the send
 313 *
 314 * Grabs ecryptfs_daemon_hash_mux.
 315 *
 316 * Returns zero on success; non-zero otherwise
 317 */
 318int ecryptfs_send_message(char *data, int data_len,
 319                          struct ecryptfs_msg_ctx **msg_ctx)
 320{
 321        int rc;
 322
 323        mutex_lock(&ecryptfs_daemon_hash_mux);
 324        rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
 325                                          msg_ctx);
 326        mutex_unlock(&ecryptfs_daemon_hash_mux);
 327        return rc;
 328}
 329
 330/**
 331 * ecryptfs_wait_for_response
 332 * @msg_ctx: The context that was assigned when sending a message
 333 * @msg: The incoming message from userspace; not set if rc != 0
 334 *
 335 * Sleeps until awaken by ecryptfs_receive_message or until the amount
 336 * of time exceeds ecryptfs_message_wait_timeout.  If zero is
 337 * returned, msg will point to a valid message from userspace; a
 338 * non-zero value is returned upon failure to receive a message or an
 339 * error occurs. Callee must free @msg on success.
 340 */
 341int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
 342                               struct ecryptfs_message **msg)
 343{
 344        signed long timeout = ecryptfs_message_wait_timeout * HZ;
 345        int rc = 0;
 346
 347sleep:
 348        timeout = schedule_timeout_interruptible(timeout);
 349        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 350        mutex_lock(&msg_ctx->mux);
 351        if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
 352                if (timeout) {
 353                        mutex_unlock(&msg_ctx->mux);
 354                        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 355                        goto sleep;
 356                }
 357                rc = -ENOMSG;
 358        } else {
 359                *msg = msg_ctx->msg;
 360                msg_ctx->msg = NULL;
 361        }
 362        ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 363        mutex_unlock(&msg_ctx->mux);
 364        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 365        return rc;
 366}
 367
 368int __init ecryptfs_init_messaging(void)
 369{
 370        int i;
 371        int rc = 0;
 372
 373        if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
 374                ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
 375                printk(KERN_WARNING "%s: Specified number of users is "
 376                       "too large, defaulting to [%d] users\n", __func__,
 377                       ecryptfs_number_of_users);
 378        }
 379        mutex_init(&ecryptfs_daemon_hash_mux);
 380        mutex_lock(&ecryptfs_daemon_hash_mux);
 381        ecryptfs_hash_bits = 1;
 382        while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
 383                ecryptfs_hash_bits++;
 384        ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
 385                                        * (1 << ecryptfs_hash_bits)),
 386                                       GFP_KERNEL);
 387        if (!ecryptfs_daemon_hash) {
 388                rc = -ENOMEM;
 389                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
 390                mutex_unlock(&ecryptfs_daemon_hash_mux);
 391                goto out;
 392        }
 393        for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
 394                INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
 395        mutex_unlock(&ecryptfs_daemon_hash_mux);
 396        ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
 397                                        * ecryptfs_message_buf_len),
 398                                       GFP_KERNEL);
 399        if (!ecryptfs_msg_ctx_arr) {
 400                rc = -ENOMEM;
 401                printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
 402                goto out;
 403        }
 404        mutex_init(&ecryptfs_msg_ctx_lists_mux);
 405        mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 406        ecryptfs_msg_counter = 0;
 407        for (i = 0; i < ecryptfs_message_buf_len; i++) {
 408                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
 409                INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
 410                mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
 411                mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 412                ecryptfs_msg_ctx_arr[i].index = i;
 413                ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
 414                ecryptfs_msg_ctx_arr[i].counter = 0;
 415                ecryptfs_msg_ctx_arr[i].task = NULL;
 416                ecryptfs_msg_ctx_arr[i].msg = NULL;
 417                list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
 418                              &ecryptfs_msg_ctx_free_list);
 419                mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 420        }
 421        mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 422        rc = ecryptfs_init_ecryptfs_miscdev();
 423        if (rc)
 424                ecryptfs_release_messaging();
 425out:
 426        return rc;
 427}
 428
 429void ecryptfs_release_messaging(void)
 430{
 431        if (ecryptfs_msg_ctx_arr) {
 432                int i;
 433
 434                mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 435                for (i = 0; i < ecryptfs_message_buf_len; i++) {
 436                        mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 437                        if (ecryptfs_msg_ctx_arr[i].msg)
 438                                kfree(ecryptfs_msg_ctx_arr[i].msg);
 439                        mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 440                }
 441                kfree(ecryptfs_msg_ctx_arr);
 442                mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 443        }
 444        if (ecryptfs_daemon_hash) {
 445                struct ecryptfs_daemon *daemon;
 446                int i;
 447
 448                mutex_lock(&ecryptfs_daemon_hash_mux);
 449                for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
 450                        int rc;
 451
 452                        hlist_for_each_entry(daemon,
 453                                             &ecryptfs_daemon_hash[i],
 454                                             euid_chain) {
 455                                rc = ecryptfs_exorcise_daemon(daemon);
 456                                if (rc)
 457                                        printk(KERN_ERR "%s: Error whilst "
 458                                               "attempting to destroy daemon; "
 459                                               "rc = [%d]. Dazed and confused, "
 460                                               "but trying to continue.\n",
 461                                               __func__, rc);
 462                        }
 463                }
 464                kfree(ecryptfs_daemon_hash);
 465                mutex_unlock(&ecryptfs_daemon_hash_mux);
 466        }
 467        ecryptfs_destroy_ecryptfs_miscdev();
 468        return;
 469}
 470
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