1 // SPDX-License-Identifier: GPL-2.0-only
2 /**
3 * eCryptfs: Linux filesystem encryption layer
4 *
5 * Copyright (C) 2004-2008 International Business Machines Corp.
6 * Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
7 * Tyler Hicks <tyhicks@ou.edu>
8 */
9 #include <linux/sched.h>
10 #include <linux/slab.h>
11 #include <linux/user_namespace.h>
12 #include <linux/nsproxy.h>
13 #include "ecryptfs_kernel.h"
14
15 static LIST_HEAD(ecryptfs_msg_ctx_free_list);
16 static LIST_HEAD(ecryptfs_msg_ctx_alloc_list);
17 static struct mutex ecryptfs_msg_ctx_lists_mux;
18
19 static struct hlist_head *ecryptfs_daemon_hash;
20 struct mutex ecryptfs_daemon_hash_mux;
21 static int ecryptfs_hash_bits;
22 #define ecryptfs_current_euid_hash(uid) \
23 hash_long((unsigned long)from_kuid(&init_user_ns, current_euid()), ecryptfs_hash_bits)
24
25 static u32 ecryptfs_msg_counter;
26 static struct ecryptfs_msg_ctx *ecryptfs_msg_ctx_arr;
27
28 /**
29 * ecryptfs_acquire_free_msg_ctx
30 * @msg_ctx: The context that was acquired from the free list
31 *
32 * Acquires a context element from the free list and locks the mutex
33 * on the context. Sets the msg_ctx task to current. Returns zero on
34 * success; non-zero on error or upon failure to acquire a free
35 * context element. Must be called with ecryptfs_msg_ctx_lists_mux
36 * held.
37 */
ecryptfs_acquire_free_msg_ctx(struct ecryptfs_msg_ctx ** msg_ctx)38 static int ecryptfs_acquire_free_msg_ctx(struct ecryptfs_msg_ctx **msg_ctx)
39 {
40 struct list_head *p;
41 int rc;
42
43 if (list_empty(&ecryptfs_msg_ctx_free_list)) {
44 printk(KERN_WARNING "%s: The eCryptfs free "
45 "context list is empty. It may be helpful to "
46 "specify the ecryptfs_message_buf_len "
47 "parameter to be greater than the current "
48 "value of [%d]\n", __func__, ecryptfs_message_buf_len);
49 rc = -ENOMEM;
50 goto out;
51 }
52 list_for_each(p, &ecryptfs_msg_ctx_free_list) {
53 *msg_ctx = list_entry(p, struct ecryptfs_msg_ctx, node);
54 if (mutex_trylock(&(*msg_ctx)->mux)) {
55 (*msg_ctx)->task = current;
56 rc = 0;
57 goto out;
58 }
59 }
60 rc = -ENOMEM;
61 out:
62 return rc;
63 }
64
65 /**
66 * ecryptfs_msg_ctx_free_to_alloc
67 * @msg_ctx: The context to move from the free list to the alloc list
68 *
69 * Must be called with ecryptfs_msg_ctx_lists_mux held.
70 */
ecryptfs_msg_ctx_free_to_alloc(struct ecryptfs_msg_ctx * msg_ctx)71 static void ecryptfs_msg_ctx_free_to_alloc(struct ecryptfs_msg_ctx *msg_ctx)
72 {
73 list_move(&msg_ctx->node, &ecryptfs_msg_ctx_alloc_list);
74 msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_PENDING;
75 msg_ctx->counter = ++ecryptfs_msg_counter;
76 }
77
78 /**
79 * ecryptfs_msg_ctx_alloc_to_free
80 * @msg_ctx: The context to move from the alloc list to the free list
81 *
82 * Must be called with ecryptfs_msg_ctx_lists_mux held.
83 */
ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx * msg_ctx)84 void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx)
85 {
86 list_move(&(msg_ctx->node), &ecryptfs_msg_ctx_free_list);
87 kfree(msg_ctx->msg);
88 msg_ctx->msg = NULL;
89 msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_FREE;
90 }
91
92 /**
93 * ecryptfs_find_daemon_by_euid
94 * @daemon: If return value is zero, points to the desired daemon pointer
95 *
96 * Must be called with ecryptfs_daemon_hash_mux held.
97 *
98 * Search the hash list for the current effective user id.
99 *
100 * Returns zero if the user id exists in the list; non-zero otherwise.
101 */
ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon ** daemon)102 int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
103 {
104 int rc;
105
106 hlist_for_each_entry(*daemon,
107 &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()],
108 euid_chain) {
109 if (uid_eq((*daemon)->file->f_cred->euid, current_euid())) {
110 rc = 0;
111 goto out;
112 }
113 }
114 rc = -EINVAL;
115 out:
116 return rc;
117 }
118
119 /**
120 * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
121 * @daemon: Pointer to set to newly allocated daemon struct
122 * @file: File used when opening /dev/ecryptfs
123 *
124 * Must be called ceremoniously while in possession of
125 * ecryptfs_sacred_daemon_hash_mux
126 *
127 * Returns zero on success; non-zero otherwise
128 */
129 int
ecryptfs_spawn_daemon(struct ecryptfs_daemon ** daemon,struct file * file)130 ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
131 {
132 int rc = 0;
133
134 (*daemon) = kzalloc(sizeof(**daemon), GFP_KERNEL);
135 if (!(*daemon)) {
136 rc = -ENOMEM;
137 goto out;
138 }
139 (*daemon)->file = file;
140 mutex_init(&(*daemon)->mux);
141 INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
142 init_waitqueue_head(&(*daemon)->wait);
143 (*daemon)->num_queued_msg_ctx = 0;
144 hlist_add_head(&(*daemon)->euid_chain,
145 &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
146 out:
147 return rc;
148 }
149
150 /**
151 * ecryptfs_exorcise_daemon - Destroy the daemon struct
152 *
153 * Must be called ceremoniously while in possession of
154 * ecryptfs_daemon_hash_mux and the daemon's own mux.
155 */
ecryptfs_exorcise_daemon(struct ecryptfs_daemon * daemon)156 int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
157 {
158 struct ecryptfs_msg_ctx *msg_ctx, *msg_ctx_tmp;
159 int rc = 0;
160
161 mutex_lock(&daemon->mux);
162 if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
163 || (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
164 rc = -EBUSY;
165 mutex_unlock(&daemon->mux);
166 goto out;
167 }
168 list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
169 &daemon->msg_ctx_out_queue, daemon_out_list) {
170 list_del(&msg_ctx->daemon_out_list);
171 daemon->num_queued_msg_ctx--;
172 printk(KERN_WARNING "%s: Warning: dropping message that is in "
173 "the out queue of a dying daemon\n", __func__);
174 ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
175 }
176 hlist_del(&daemon->euid_chain);
177 mutex_unlock(&daemon->mux);
178 kzfree(daemon);
179 out:
180 return rc;
181 }
182
183 /**
184 * ecryptfs_process_reponse
185 * @msg: The ecryptfs message received; the caller should sanity check
186 * msg->data_len and free the memory
187 * @seq: The sequence number of the message; must match the sequence
188 * number for the existing message context waiting for this
189 * response
190 *
191 * Processes a response message after sending an operation request to
192 * userspace. Some other process is awaiting this response. Before
193 * sending out its first communications, the other process allocated a
194 * msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
195 * response message contains this index so that we can copy over the
196 * response message into the msg_ctx that the process holds a
197 * reference to. The other process is going to wake up, check to see
198 * that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
199 * proceed to read off and process the response message. Returns zero
200 * upon delivery to desired context element; non-zero upon delivery
201 * failure or error.
202 *
203 * Returns zero on success; non-zero otherwise
204 */
ecryptfs_process_response(struct ecryptfs_daemon * daemon,struct ecryptfs_message * msg,u32 seq)205 int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
206 struct ecryptfs_message *msg, u32 seq)
207 {
208 struct ecryptfs_msg_ctx *msg_ctx;
209 size_t msg_size;
210 int rc;
211
212 if (msg->index >= ecryptfs_message_buf_len) {
213 rc = -EINVAL;
214 printk(KERN_ERR "%s: Attempt to reference "
215 "context buffer at index [%d]; maximum "
216 "allowable is [%d]\n", __func__, msg->index,
217 (ecryptfs_message_buf_len - 1));
218 goto out;
219 }
220 msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
221 mutex_lock(&msg_ctx->mux);
222 if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
223 rc = -EINVAL;
224 printk(KERN_WARNING "%s: Desired context element is not "
225 "pending a response\n", __func__);
226 goto unlock;
227 } else if (msg_ctx->counter != seq) {
228 rc = -EINVAL;
229 printk(KERN_WARNING "%s: Invalid message sequence; "
230 "expected [%d]; received [%d]\n", __func__,
231 msg_ctx->counter, seq);
232 goto unlock;
233 }
234 msg_size = (sizeof(*msg) + msg->data_len);
235 msg_ctx->msg = kmemdup(msg, msg_size, GFP_KERNEL);
236 if (!msg_ctx->msg) {
237 rc = -ENOMEM;
238 goto unlock;
239 }
240 msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
241 wake_up_process(msg_ctx->task);
242 rc = 0;
243 unlock:
244 mutex_unlock(&msg_ctx->mux);
245 out:
246 return rc;
247 }
248
249 /**
250 * ecryptfs_send_message_locked
251 * @data: The data to send
252 * @data_len: The length of data
253 * @msg_ctx: The message context allocated for the send
254 *
255 * Must be called with ecryptfs_daemon_hash_mux held.
256 *
257 * Returns zero on success; non-zero otherwise
258 */
259 static int
ecryptfs_send_message_locked(char * data,int data_len,u8 msg_type,struct ecryptfs_msg_ctx ** msg_ctx)260 ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
261 struct ecryptfs_msg_ctx **msg_ctx)
262 {
263 struct ecryptfs_daemon *daemon;
264 int rc;
265
266 rc = ecryptfs_find_daemon_by_euid(&daemon);
267 if (rc) {
268 rc = -ENOTCONN;
269 goto out;
270 }
271 mutex_lock(&ecryptfs_msg_ctx_lists_mux);
272 rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
273 if (rc) {
274 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
275 printk(KERN_WARNING "%s: Could not claim a free "
276 "context element\n", __func__);
277 goto out;
278 }
279 ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
280 mutex_unlock(&(*msg_ctx)->mux);
281 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
282 rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
283 daemon);
284 if (rc)
285 printk(KERN_ERR "%s: Error attempting to send message to "
286 "userspace daemon; rc = [%d]\n", __func__, rc);
287 out:
288 return rc;
289 }
290
291 /**
292 * ecryptfs_send_message
293 * @data: The data to send
294 * @data_len: The length of data
295 * @msg_ctx: The message context allocated for the send
296 *
297 * Grabs ecryptfs_daemon_hash_mux.
298 *
299 * Returns zero on success; non-zero otherwise
300 */
ecryptfs_send_message(char * data,int data_len,struct ecryptfs_msg_ctx ** msg_ctx)301 int ecryptfs_send_message(char *data, int data_len,
302 struct ecryptfs_msg_ctx **msg_ctx)
303 {
304 int rc;
305
306 mutex_lock(&ecryptfs_daemon_hash_mux);
307 rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
308 msg_ctx);
309 mutex_unlock(&ecryptfs_daemon_hash_mux);
310 return rc;
311 }
312
313 /**
314 * ecryptfs_wait_for_response
315 * @msg_ctx: The context that was assigned when sending a message
316 * @msg: The incoming message from userspace; not set if rc != 0
317 *
318 * Sleeps until awaken by ecryptfs_receive_message or until the amount
319 * of time exceeds ecryptfs_message_wait_timeout. If zero is
320 * returned, msg will point to a valid message from userspace; a
321 * non-zero value is returned upon failure to receive a message or an
322 * error occurs. Callee must free @msg on success.
323 */
ecryptfs_wait_for_response(struct ecryptfs_msg_ctx * msg_ctx,struct ecryptfs_message ** msg)324 int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
325 struct ecryptfs_message **msg)
326 {
327 signed long timeout = ecryptfs_message_wait_timeout * HZ;
328 int rc = 0;
329
330 sleep:
331 timeout = schedule_timeout_interruptible(timeout);
332 mutex_lock(&ecryptfs_msg_ctx_lists_mux);
333 mutex_lock(&msg_ctx->mux);
334 if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
335 if (timeout) {
336 mutex_unlock(&msg_ctx->mux);
337 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
338 goto sleep;
339 }
340 rc = -ENOMSG;
341 } else {
342 *msg = msg_ctx->msg;
343 msg_ctx->msg = NULL;
344 }
345 ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
346 mutex_unlock(&msg_ctx->mux);
347 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
348 return rc;
349 }
350
ecryptfs_init_messaging(void)351 int __init ecryptfs_init_messaging(void)
352 {
353 int i;
354 int rc = 0;
355
356 if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
357 ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
358 printk(KERN_WARNING "%s: Specified number of users is "
359 "too large, defaulting to [%d] users\n", __func__,
360 ecryptfs_number_of_users);
361 }
362 mutex_init(&ecryptfs_daemon_hash_mux);
363 mutex_lock(&ecryptfs_daemon_hash_mux);
364 ecryptfs_hash_bits = 1;
365 while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
366 ecryptfs_hash_bits++;
367 ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
368 * (1 << ecryptfs_hash_bits)),
369 GFP_KERNEL);
370 if (!ecryptfs_daemon_hash) {
371 rc = -ENOMEM;
372 mutex_unlock(&ecryptfs_daemon_hash_mux);
373 goto out;
374 }
375 for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
376 INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
377 mutex_unlock(&ecryptfs_daemon_hash_mux);
378 ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
379 * ecryptfs_message_buf_len),
380 GFP_KERNEL);
381 if (!ecryptfs_msg_ctx_arr) {
382 rc = -ENOMEM;
383 goto out;
384 }
385 mutex_init(&ecryptfs_msg_ctx_lists_mux);
386 mutex_lock(&ecryptfs_msg_ctx_lists_mux);
387 ecryptfs_msg_counter = 0;
388 for (i = 0; i < ecryptfs_message_buf_len; i++) {
389 INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
390 INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
391 mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
392 mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
393 ecryptfs_msg_ctx_arr[i].index = i;
394 ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
395 ecryptfs_msg_ctx_arr[i].counter = 0;
396 ecryptfs_msg_ctx_arr[i].task = NULL;
397 ecryptfs_msg_ctx_arr[i].msg = NULL;
398 list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
399 &ecryptfs_msg_ctx_free_list);
400 mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
401 }
402 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
403 rc = ecryptfs_init_ecryptfs_miscdev();
404 if (rc)
405 ecryptfs_release_messaging();
406 out:
407 return rc;
408 }
409
ecryptfs_release_messaging(void)410 void ecryptfs_release_messaging(void)
411 {
412 if (ecryptfs_msg_ctx_arr) {
413 int i;
414
415 mutex_lock(&ecryptfs_msg_ctx_lists_mux);
416 for (i = 0; i < ecryptfs_message_buf_len; i++) {
417 mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
418 kfree(ecryptfs_msg_ctx_arr[i].msg);
419 mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
420 }
421 kfree(ecryptfs_msg_ctx_arr);
422 mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
423 }
424 if (ecryptfs_daemon_hash) {
425 struct ecryptfs_daemon *daemon;
426 struct hlist_node *n;
427 int i;
428
429 mutex_lock(&ecryptfs_daemon_hash_mux);
430 for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
431 int rc;
432
433 hlist_for_each_entry_safe(daemon, n,
434 &ecryptfs_daemon_hash[i],
435 euid_chain) {
436 rc = ecryptfs_exorcise_daemon(daemon);
437 if (rc)
438 printk(KERN_ERR "%s: Error whilst "
439 "attempting to destroy daemon; "
440 "rc = [%d]. Dazed and confused, "
441 "but trying to continue.\n",
442 __func__, rc);
443 }
444 }
445 kfree(ecryptfs_daemon_hash);
446 mutex_unlock(&ecryptfs_daemon_hash_mux);
447 }
448 ecryptfs_destroy_ecryptfs_miscdev();
449 return;
450 }
451