summaryrefslogtreecommitdiffstats
path: root/fs/ecryptfs/messaging.c
blob: 8646ba76def3416b141f8fe4f54a5812302e7886 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
// SPDX-License-Identifier: GPL-2.0-only
/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2004-2008 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
 *		Tyler Hicks <code@tyhicks.com>
 */
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/user_namespace.h>
#include <linux/nsproxy.h>
#include "ecryptfs_kernel.h"

static LIST_HEAD(ecryptfs_msg_ctx_free_list);
static LIST_HEAD(ecryptfs_msg_ctx_alloc_list);
static struct mutex ecryptfs_msg_ctx_lists_mux;

static struct hlist_head *ecryptfs_daemon_hash;
struct mutex ecryptfs_daemon_hash_mux;
static int ecryptfs_hash_bits;
#define ecryptfs_current_euid_hash(uid) \
	hash_long((unsigned long)from_kuid(&init_user_ns, current_euid()), ecryptfs_hash_bits)

static u32 ecryptfs_msg_counter;
static struct ecryptfs_msg_ctx *ecryptfs_msg_ctx_arr;

/**
 * ecryptfs_acquire_free_msg_ctx
 * @msg_ctx: The context that was acquired from the free list
 *
 * Acquires a context element from the free list and locks the mutex
 * on the context.  Sets the msg_ctx task to current.  Returns zero on
 * success; non-zero on error or upon failure to acquire a free
 * context element.  Must be called with ecryptfs_msg_ctx_lists_mux
 * held.
 */
static int ecryptfs_acquire_free_msg_ctx(struct ecryptfs_msg_ctx **msg_ctx)
{
	struct list_head *p;
	int rc;

	if (list_empty(&ecryptfs_msg_ctx_free_list)) {
		printk(KERN_WARNING "%s: The eCryptfs free "
		       "context list is empty.  It may be helpful to "
		       "specify the ecryptfs_message_buf_len "
		       "parameter to be greater than the current "
		       "value of [%d]\n", __func__, ecryptfs_message_buf_len);
		rc = -ENOMEM;
		goto out;
	}
	list_for_each(p, &ecryptfs_msg_ctx_free_list) {
		*msg_ctx = list_entry(p, struct ecryptfs_msg_ctx, node);
		if (mutex_trylock(&(*msg_ctx)->mux)) {
			(*msg_ctx)->task = current;
			rc = 0;
			goto out;
		}
	}
	rc = -ENOMEM;
out:
	return rc;
}

/**
 * ecryptfs_msg_ctx_free_to_alloc
 * @msg_ctx: The context to move from the free list to the alloc list
 *
 * Must be called with ecryptfs_msg_ctx_lists_mux held.
 */
static void ecryptfs_msg_ctx_free_to_alloc(struct ecryptfs_msg_ctx *msg_ctx)
{
	list_move(&msg_ctx->node, &ecryptfs_msg_ctx_alloc_list);
	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_PENDING;
	msg_ctx->counter = ++ecryptfs_msg_counter;
}

/**
 * ecryptfs_msg_ctx_alloc_to_free
 * @msg_ctx: The context to move from the alloc list to the free list
 *
 * Must be called with ecryptfs_msg_ctx_lists_mux held.
 */
void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx)
{
	list_move(&(msg_ctx->node), &ecryptfs_msg_ctx_free_list);
	kfree(msg_ctx->msg);
	msg_ctx->msg = NULL;
	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_FREE;
}

/**
 * ecryptfs_find_daemon_by_euid
 * @daemon: If return value is zero, points to the desired daemon pointer
 *
 * Must be called with ecryptfs_daemon_hash_mux held.
 *
 * Search the hash list for the current effective user id.
 *
 * Returns zero if the user id exists in the list; non-zero otherwise.
 */
int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
{
	int rc;

	hlist_for_each_entry(*daemon,
			    &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()],
			    euid_chain) {
		if (uid_eq((*daemon)->file->f_cred->euid, current_euid())) {
			rc = 0;
			goto out;
		}
	}
	rc = -EINVAL;
out:
	return rc;
}

/**
 * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
 * @daemon: Pointer to set to newly allocated daemon struct
 * @file: File used when opening /dev/ecryptfs
 *
 * Must be called ceremoniously while in possession of
 * ecryptfs_sacred_daemon_hash_mux
 *
 * Returns zero on success; non-zero otherwise
 */
int
ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
{
	int rc = 0;

	(*daemon) = kzalloc(sizeof(**daemon), GFP_KERNEL);
	if (!(*daemon)) {
		rc = -ENOMEM;
		goto out;
	}
	(*daemon)->file = file;
	mutex_init(&(*daemon)->mux);
	INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
	init_waitqueue_head(&(*daemon)->wait);
	(*daemon)->num_queued_msg_ctx = 0;
	hlist_add_head(&(*daemon)->euid_chain,
		       &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
out:
	return rc;
}

/**
 * ecryptfs_exorcise_daemon - Destroy the daemon struct
 *
 * Must be called ceremoniously while in possession of
 * ecryptfs_daemon_hash_mux and the daemon's own mux.
 */
int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
{
	struct ecryptfs_msg_ctx *msg_ctx, *msg_ctx_tmp;
	int rc = 0;

	mutex_lock(&daemon->mux);
	if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
	    || (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
		rc = -EBUSY;
		mutex_unlock(&daemon->mux);
		goto out;
	}
	list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
				 &daemon->msg_ctx_out_queue, daemon_out_list) {
		list_del(&msg_ctx->daemon_out_list);
		daemon->num_queued_msg_ctx--;
		printk(KERN_WARNING "%s: Warning: dropping message that is in "
		       "the out queue of a dying daemon\n", __func__);
		ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
	}
	hlist_del(&daemon->euid_chain);
	mutex_unlock(&daemon->mux);
	kzfree(daemon);
out:
	return rc;
}

/**
 * ecryptfs_process_reponse
 * @msg: The ecryptfs message received; the caller should sanity check
 *       msg->data_len and free the memory
 * @seq: The sequence number of the message; must match the sequence
 *       number for the existing message context waiting for this
 *       response
 *
 * Processes a response message after sending an operation request to
 * userspace. Some other process is awaiting this response. Before
 * sending out its first communications, the other process allocated a
 * msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
 * response message contains this index so that we can copy over the
 * response message into the msg_ctx that the process holds a
 * reference to. The other process is going to wake up, check to see
 * that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
 * proceed to read off and process the response message. Returns zero
 * upon delivery to desired context element; non-zero upon delivery
 * failure or error.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
			      struct ecryptfs_message *msg, u32 seq)
{
	struct ecryptfs_msg_ctx *msg_ctx;
	size_t msg_size;
	int rc;

	if (msg->index >= ecryptfs_message_buf_len) {
		rc = -EINVAL;
		printk(KERN_ERR "%s: Attempt to reference "
		       "context buffer at index [%d]; maximum "
		       "allowable is [%d]\n", __func__, msg->index,
		       (ecryptfs_message_buf_len - 1));
		goto out;
	}
	msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
	mutex_lock(&msg_ctx->mux);
	if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
		rc = -EINVAL;
		printk(KERN_WARNING "%s: Desired context element is not "
		       "pending a response\n", __func__);
		goto unlock;
	} else if (msg_ctx->counter != seq) {
		rc = -EINVAL;
		printk(KERN_WARNING "%s: Invalid message sequence; "
		       "expected [%d]; received [%d]\n", __func__,
		       msg_ctx->counter, seq);
		goto unlock;
	}
	msg_size = (sizeof(*msg) + msg->data_len);
	msg_ctx->msg = kmemdup(msg, msg_size, GFP_KERNEL);
	if (!msg_ctx->msg) {
		rc = -ENOMEM;
		goto unlock;
	}
	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
	wake_up_process(msg_ctx->task);
	rc = 0;
unlock:
	mutex_unlock(&msg_ctx->mux);
out:
	return rc;
}

/**
 * ecryptfs_send_message_locked
 * @data: The data to send
 * @data_len: The length of data
 * @msg_ctx: The message context allocated for the send
 *
 * Must be called with ecryptfs_daemon_hash_mux held.
 *
 * Returns zero on success; non-zero otherwise
 */
static int
ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
			     struct ecryptfs_msg_ctx **msg_ctx)
{
	struct ecryptfs_daemon *daemon;
	int rc;

	rc = ecryptfs_find_daemon_by_euid(&daemon);
	if (rc) {
		rc = -ENOTCONN;
		goto out;
	}
	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
	rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
	if (rc) {
		mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
		printk(KERN_WARNING "%s: Could not claim a free "
		       "context element\n", __func__);
		goto out;
	}
	ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
	mutex_unlock(&(*msg_ctx)->mux);
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
				   daemon);
	if (rc)
		printk(KERN_ERR "%s: Error attempting to send message to "
		       "userspace daemon; rc = [%d]\n", __func__, rc);
out:
	return rc;
}

/**
 * ecryptfs_send_message
 * @data: The data to send
 * @data_len: The length of data
 * @msg_ctx: The message context allocated for the send
 *
 * Grabs ecryptfs_daemon_hash_mux.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_send_message(char *data, int data_len,
			  struct ecryptfs_msg_ctx **msg_ctx)
{
	int rc;

	mutex_lock(&ecryptfs_daemon_hash_mux);
	rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
					  msg_ctx);
	mutex_unlock(&ecryptfs_daemon_hash_mux);
	return rc;
}

/**
 * ecryptfs_wait_for_response
 * @msg_ctx: The context that was assigned when sending a message
 * @msg: The incoming message from userspace; not set if rc != 0
 *
 * Sleeps until awaken by ecryptfs_receive_message or until the amount
 * of time exceeds ecryptfs_message_wait_timeout.  If zero is
 * returned, msg will point to a valid message from userspace; a
 * non-zero value is returned upon failure to receive a message or an
 * error occurs. Callee must free @msg on success.
 */
int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
			       struct ecryptfs_message **msg)
{
	signed long timeout = ecryptfs_message_wait_timeout * HZ;
	int rc = 0;

sleep:
	timeout = schedule_timeout_interruptible(timeout);
	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
	mutex_lock(&msg_ctx->mux);
	if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
		if (timeout) {
			mutex_unlock(&msg_ctx->mux);
			mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
			goto sleep;
		}
		rc = -ENOMSG;
	} else {
		*msg = msg_ctx->msg;
		msg_ctx->msg = NULL;
	}
	ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
	mutex_unlock(&msg_ctx->mux);
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	return rc;
}

int __init ecryptfs_init_messaging(void)
{
	int i;
	int rc = 0;

	if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
		ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
		printk(KERN_WARNING "%s: Specified number of users is "
		       "too large, defaulting to [%d] users\n", __func__,
		       ecryptfs_number_of_users);
	}
	mutex_init(&ecryptfs_daemon_hash_mux);
	mutex_lock(&ecryptfs_daemon_hash_mux);
	ecryptfs_hash_bits = 1;
	while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
		ecryptfs_hash_bits++;
	ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
					* (1 << ecryptfs_hash_bits)),
				       GFP_KERNEL);
	if (!ecryptfs_daemon_hash) {
		rc = -ENOMEM;
		mutex_unlock(&ecryptfs_daemon_hash_mux);
		goto out;
	}
	for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
		INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
	mutex_unlock(&ecryptfs_daemon_hash_mux);
	ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
					* ecryptfs_message_buf_len),
				       GFP_KERNEL);
	if (!ecryptfs_msg_ctx_arr) {
		kfree(ecryptfs_daemon_hash);
		rc = -ENOMEM;
		goto out;
	}
	mutex_init(&ecryptfs_msg_ctx_lists_mux);
	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
	ecryptfs_msg_counter = 0;
	for (i = 0; i < ecryptfs_message_buf_len; i++) {
		INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
		INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
		mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
		mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
		ecryptfs_msg_ctx_arr[i].index = i;
		ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
		ecryptfs_msg_ctx_arr[i].counter = 0;
		ecryptfs_msg_ctx_arr[i].task = NULL;
		ecryptfs_msg_ctx_arr[i].msg = NULL;
		list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
			      &ecryptfs_msg_ctx_free_list);
		mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
	}
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	rc = ecryptfs_init_ecryptfs_miscdev();
	if (rc)
		ecryptfs_release_messaging();
out:
	return rc;
}

void ecryptfs_release_messaging(void)
{
	if (ecryptfs_msg_ctx_arr) {
		int i;

		mutex_lock(&ecryptfs_msg_ctx_lists_mux);
		for (i = 0; i < ecryptfs_message_buf_len; i++) {
			mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
			kfree(ecryptfs_msg_ctx_arr[i].msg);
			mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
		}
		kfree(ecryptfs_msg_ctx_arr);
		mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	}
	if (ecryptfs_daemon_hash) {
		struct ecryptfs_daemon *daemon;
		struct hlist_node *n;
		int i;

		mutex_lock(&ecryptfs_daemon_hash_mux);
		for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
			int rc;

			hlist_for_each_entry_safe(daemon, n,
						  &ecryptfs_daemon_hash[i],
						  euid_chain) {
				rc = ecryptfs_exorcise_daemon(daemon);
				if (rc)
					printk(KERN_ERR "%s: Error whilst "
					       "attempting to destroy daemon; "
					       "rc = [%d]. Dazed and confused, "
					       "but trying to continue.\n",
					       __func__, rc);
			}
		}
		kfree(ecryptfs_daemon_hash);
		mutex_unlock(&ecryptfs_daemon_hash_mux);
	}
	ecryptfs_destroy_ecryptfs_miscdev();
	return;
}