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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 = kmalloc(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         memcpy(msg_ctx->msg, msg, msg_size);
258         msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
259         wake_up_process(msg_ctx->task);
260         rc = 0;
261 unlock:
262         mutex_unlock(&msg_ctx->mux);
263 out:
264         return rc;
265 }
266 
267 /**
268  * ecryptfs_send_message_locked
269  * @data: The data to send
270  * @data_len: The length of data
271  * @msg_ctx: The message context allocated for the send
272  *
273  * Must be called with ecryptfs_daemon_hash_mux held.
274  *
275  * Returns zero on success; non-zero otherwise
276  */
277 static int
278 ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
279                              struct ecryptfs_msg_ctx **msg_ctx)
280 {
281         struct ecryptfs_daemon *daemon;
282         int rc;
283 
284         rc = ecryptfs_find_daemon_by_euid(&daemon);
285         if (rc) {
286                 rc = -ENOTCONN;
287                 goto out;
288         }
289         mutex_lock(&ecryptfs_msg_ctx_lists_mux);
290         rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
291         if (rc) {
292                 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
293                 printk(KERN_WARNING "%s: Could not claim a free "
294                        "context element\n", __func__);
295                 goto out;
296         }
297         ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
298         mutex_unlock(&(*msg_ctx)->mux);
299         mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
300         rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
301                                    daemon);
302         if (rc)
303                 printk(KERN_ERR "%s: Error attempting to send message to "
304                        "userspace daemon; rc = [%d]\n", __func__, rc);
305 out:
306         return rc;
307 }
308 
309 /**
310  * ecryptfs_send_message
311  * @data: The data to send
312  * @data_len: The length of data
313  * @msg_ctx: The message context allocated for the send
314  *
315  * Grabs ecryptfs_daemon_hash_mux.
316  *
317  * Returns zero on success; non-zero otherwise
318  */
319 int ecryptfs_send_message(char *data, int data_len,
320                           struct ecryptfs_msg_ctx **msg_ctx)
321 {
322         int rc;
323 
324         mutex_lock(&ecryptfs_daemon_hash_mux);
325         rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
326                                           msg_ctx);
327         mutex_unlock(&ecryptfs_daemon_hash_mux);
328         return rc;
329 }
330 
331 /**
332  * ecryptfs_wait_for_response
333  * @msg_ctx: The context that was assigned when sending a message
334  * @msg: The incoming message from userspace; not set if rc != 0
335  *
336  * Sleeps until awaken by ecryptfs_receive_message or until the amount
337  * of time exceeds ecryptfs_message_wait_timeout.  If zero is
338  * returned, msg will point to a valid message from userspace; a
339  * non-zero value is returned upon failure to receive a message or an
340  * error occurs. Callee must free @msg on success.
341  */
342 int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
343                                struct ecryptfs_message **msg)
344 {
345         signed long timeout = ecryptfs_message_wait_timeout * HZ;
346         int rc = 0;
347 
348 sleep:
349         timeout = schedule_timeout_interruptible(timeout);
350         mutex_lock(&ecryptfs_msg_ctx_lists_mux);
351         mutex_lock(&msg_ctx->mux);
352         if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
353                 if (timeout) {
354                         mutex_unlock(&msg_ctx->mux);
355                         mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
356                         goto sleep;
357                 }
358                 rc = -ENOMSG;
359         } else {
360                 *msg = msg_ctx->msg;
361                 msg_ctx->msg = NULL;
362         }
363         ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
364         mutex_unlock(&msg_ctx->mux);
365         mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
366         return rc;
367 }
368 
369 int __init ecryptfs_init_messaging(void)
370 {
371         int i;
372         int rc = 0;
373 
374         if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
375                 ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
376                 printk(KERN_WARNING "%s: Specified number of users is "
377                        "too large, defaulting to [%d] users\n", __func__,
378                        ecryptfs_number_of_users);
379         }
380         mutex_init(&ecryptfs_daemon_hash_mux);
381         mutex_lock(&ecryptfs_daemon_hash_mux);
382         ecryptfs_hash_bits = 1;
383         while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
384                 ecryptfs_hash_bits++;
385         ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
386                                         * (1 << ecryptfs_hash_bits)),
387                                        GFP_KERNEL);
388         if (!ecryptfs_daemon_hash) {
389                 rc = -ENOMEM;
390                 printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
391                 mutex_unlock(&ecryptfs_daemon_hash_mux);
392                 goto out;
393         }
394         for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
395                 INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
396         mutex_unlock(&ecryptfs_daemon_hash_mux);
397         ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
398                                         * ecryptfs_message_buf_len),
399                                        GFP_KERNEL);
400         if (!ecryptfs_msg_ctx_arr) {
401                 rc = -ENOMEM;
402                 printk(KERN_ERR "%s: Failed to allocate memory\n", __func__);
403                 goto out;
404         }
405         mutex_init(&ecryptfs_msg_ctx_lists_mux);
406         mutex_lock(&ecryptfs_msg_ctx_lists_mux);
407         ecryptfs_msg_counter = 0;
408         for (i = 0; i < ecryptfs_message_buf_len; i++) {
409                 INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
410                 INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
411                 mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
412                 mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
413                 ecryptfs_msg_ctx_arr[i].index = i;
414                 ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
415                 ecryptfs_msg_ctx_arr[i].counter = 0;
416                 ecryptfs_msg_ctx_arr[i].task = NULL;
417                 ecryptfs_msg_ctx_arr[i].msg = NULL;
418                 list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
419                               &ecryptfs_msg_ctx_free_list);
420                 mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
421         }
422         mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
423         rc = ecryptfs_init_ecryptfs_miscdev();
424         if (rc)
425                 ecryptfs_release_messaging();
426 out:
427         return rc;
428 }
429 
430 void ecryptfs_release_messaging(void)
431 {
432         if (ecryptfs_msg_ctx_arr) {
433                 int i;
434 
435                 mutex_lock(&ecryptfs_msg_ctx_lists_mux);
436                 for (i = 0; i < ecryptfs_message_buf_len; i++) {
437                         mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
438                         if (ecryptfs_msg_ctx_arr[i].msg)
439                                 kfree(ecryptfs_msg_ctx_arr[i].msg);
440                         mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
441                 }
442                 kfree(ecryptfs_msg_ctx_arr);
443                 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
444         }
445         if (ecryptfs_daemon_hash) {
446                 struct ecryptfs_daemon *daemon;
447                 int i;
448 
449                 mutex_lock(&ecryptfs_daemon_hash_mux);
450                 for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
451                         int rc;
452 
453                         hlist_for_each_entry(daemon,
454                                              &ecryptfs_daemon_hash[i],
455                                              euid_chain) {
456                                 rc = ecryptfs_exorcise_daemon(daemon);
457                                 if (rc)
458                                         printk(KERN_ERR "%s: Error whilst "
459                                                "attempting to destroy daemon; "
460                                                "rc = [%d]. Dazed and confused, "
461                                                "but trying to continue.\n",
462                                                __func__, rc);
463                         }
464                 }
465                 kfree(ecryptfs_daemon_hash);
466                 mutex_unlock(&ecryptfs_daemon_hash_mux);
467         }
468         ecryptfs_destroy_ecryptfs_miscdev();
469         return;
470 }
471 

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