fs/ecryptfs/messaging.c

   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
  28 static LIST_HEAD(ecryptfs_msg_ctx_free_list);
  29 static LIST_HEAD(ecryptfs_msg_ctx_alloc_list);
  30 static struct mutex ecryptfs_msg_ctx_lists_mux;
  31
  32 static struct hlist_head *ecryptfs_daemon_hash;
  33 struct mutex ecryptfs_daemon_hash_mux;
  34 static int ecryptfs_hash_bits;
  35 #define ecryptfs_current_euid_hash(uid) \
  36                 hash_long((unsigned long)current_euid(), ecryptfs_hash_bits)
  37
  38 static u32 ecryptfs_msg_counter;
  39 static 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  */
  51 static 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;
  74 out:
  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  */
  84 static 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  */
  97 void 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  */
 116 int 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;
 131 out:
 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  */
 145 int
 146 ecryptfs_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()]);
 164 out:
 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  */
 174 int 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);
 197 out:
 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  */
 223 int 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;
 264 unlock:
 265         mutex_unlock(&msg_ctx->mux);
 266 out:
 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  */
 280 static int
 281 ecryptfs_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);
 308 out:
 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  */
 322 int 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  */
 345 int 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
 351 sleep:
 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
 372 int __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();
 429 out:
 430         return rc;
 431 }
 432
 433 void 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 }