xref: /linux/fs/ecryptfs/messaging.c (revision 827634added7f38b7d724cab1dccdb2b004c13c3)
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