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TOMOYO Linux Cross Reference
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 
 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)from_kuid(&init_user_ns, 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         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  */
115 int 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;
128 out:
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  */
142 int
143 ecryptfs_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()]);
161 out:
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  */
171 int 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);
194 out:
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  */
220 int 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;
260 unlock:
261         mutex_unlock(&msg_ctx->mux);
262 out:
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  */
276 static int
277 ecryptfs_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);
304 out:
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  */
318 int 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  */
341 int 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 
347 sleep:
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 
368 int __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();
425 out:
426         return rc;
427 }
428 
429 void 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                         kfree(ecryptfs_msg_ctx_arr[i].msg);
438                         mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
439                 }
440                 kfree(ecryptfs_msg_ctx_arr);
441                 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
442         }
443         if (ecryptfs_daemon_hash) {
444                 struct ecryptfs_daemon *daemon;
445                 int i;
446 
447                 mutex_lock(&ecryptfs_daemon_hash_mux);
448                 for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
449                         int rc;
450 
451                         hlist_for_each_entry(daemon,
452                                              &ecryptfs_daemon_hash[i],
453                                              euid_chain) {
454                                 rc = ecryptfs_exorcise_daemon(daemon);
455                                 if (rc)
456                                         printk(KERN_ERR "%s: Error whilst "
457                                                "attempting to destroy daemon; "
458                                                "rc = [%d]. Dazed and confused, "
459                                                "but trying to continue.\n",
460                                                __func__, rc);
461                         }
462                 }
463                 kfree(ecryptfs_daemon_hash);
464                 mutex_unlock(&ecryptfs_daemon_hash_mux);
465         }
466         ecryptfs_destroy_ecryptfs_miscdev();
467         return;
468 }
469 

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