xref: /linux/fs/ecryptfs/messaging.c (revision 4413e16d9d21673bb5048a2e542f1aaa00015c2e)
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 }
475