xref: /openbmc/linux/fs/ecryptfs/miscdev.c (revision 65bbb7b8)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * eCryptfs: Linux filesystem encryption layer
4  *
5  * Copyright (C) 2008 International Business Machines Corp.
6  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
7  */
8 
9 #include <linux/fs.h>
10 #include <linux/hash.h>
11 #include <linux/random.h>
12 #include <linux/miscdevice.h>
13 #include <linux/poll.h>
14 #include <linux/slab.h>
15 #include <linux/wait.h>
16 #include <linux/module.h>
17 #include "ecryptfs_kernel.h"
18 
19 static atomic_t ecryptfs_num_miscdev_opens;
20 
21 /**
22  * ecryptfs_miscdev_poll
23  * @file: dev file
24  * @pt: dev poll table (ignored)
25  *
26  * Returns the poll mask
27  */
28 static __poll_t
ecryptfs_miscdev_poll(struct file * file,poll_table * pt)29 ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
30 {
31 	struct ecryptfs_daemon *daemon = file->private_data;
32 	__poll_t mask = 0;
33 
34 	mutex_lock(&daemon->mux);
35 	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
36 		printk(KERN_WARNING "%s: Attempt to poll on zombified "
37 		       "daemon\n", __func__);
38 		goto out_unlock_daemon;
39 	}
40 	if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
41 		goto out_unlock_daemon;
42 	if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
43 		goto out_unlock_daemon;
44 	daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
45 	mutex_unlock(&daemon->mux);
46 	poll_wait(file, &daemon->wait, pt);
47 	mutex_lock(&daemon->mux);
48 	if (!list_empty(&daemon->msg_ctx_out_queue))
49 		mask |= EPOLLIN | EPOLLRDNORM;
50 out_unlock_daemon:
51 	daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
52 	mutex_unlock(&daemon->mux);
53 	return mask;
54 }
55 
56 /**
57  * ecryptfs_miscdev_open
58  * @inode: inode of miscdev handle (ignored)
59  * @file: file for miscdev handle
60  *
61  * Returns zero on success; non-zero otherwise
62  */
63 static int
ecryptfs_miscdev_open(struct inode * inode,struct file * file)64 ecryptfs_miscdev_open(struct inode *inode, struct file *file)
65 {
66 	struct ecryptfs_daemon *daemon = NULL;
67 	int rc;
68 
69 	mutex_lock(&ecryptfs_daemon_hash_mux);
70 	rc = ecryptfs_find_daemon_by_euid(&daemon);
71 	if (!rc) {
72 		rc = -EINVAL;
73 		goto out_unlock_daemon_list;
74 	}
75 	rc = ecryptfs_spawn_daemon(&daemon, file);
76 	if (rc) {
77 		printk(KERN_ERR "%s: Error attempting to spawn daemon; "
78 		       "rc = [%d]\n", __func__, rc);
79 		goto out_unlock_daemon_list;
80 	}
81 	mutex_lock(&daemon->mux);
82 	if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
83 		rc = -EBUSY;
84 		goto out_unlock_daemon;
85 	}
86 	daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
87 	file->private_data = daemon;
88 	atomic_inc(&ecryptfs_num_miscdev_opens);
89 out_unlock_daemon:
90 	mutex_unlock(&daemon->mux);
91 out_unlock_daemon_list:
92 	mutex_unlock(&ecryptfs_daemon_hash_mux);
93 	return rc;
94 }
95 
96 /**
97  * ecryptfs_miscdev_release
98  * @inode: inode of fs/ecryptfs/euid handle (ignored)
99  * @file: file for fs/ecryptfs/euid handle
100  *
101  * This keeps the daemon registered until the daemon sends another
102  * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
103  *
104  * Returns zero on success; non-zero otherwise
105  */
106 static int
ecryptfs_miscdev_release(struct inode * inode,struct file * file)107 ecryptfs_miscdev_release(struct inode *inode, struct file *file)
108 {
109 	struct ecryptfs_daemon *daemon = file->private_data;
110 	int rc;
111 
112 	mutex_lock(&daemon->mux);
113 	BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
114 	daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
115 	atomic_dec(&ecryptfs_num_miscdev_opens);
116 	mutex_unlock(&daemon->mux);
117 
118 	mutex_lock(&ecryptfs_daemon_hash_mux);
119 	rc = ecryptfs_exorcise_daemon(daemon);
120 	mutex_unlock(&ecryptfs_daemon_hash_mux);
121 	if (rc) {
122 		printk(KERN_CRIT "%s: Fatal error whilst attempting to "
123 		       "shut down daemon; rc = [%d]. Please report this "
124 		       "bug.\n", __func__, rc);
125 		BUG();
126 	}
127 	return rc;
128 }
129 
130 /**
131  * ecryptfs_send_miscdev
132  * @data: Data to send to daemon; may be NULL
133  * @data_size: Amount of data to send to daemon
134  * @msg_ctx: Message context, which is used to handle the reply. If
135  *           this is NULL, then we do not expect a reply.
136  * @msg_type: Type of message
137  * @msg_flags: Flags for message
138  * @daemon: eCryptfs daemon object
139  *
140  * Add msg_ctx to queue and then, if it exists, notify the blocked
141  * miscdevess about the data being available. Must be called with
142  * ecryptfs_daemon_hash_mux held.
143  *
144  * Returns zero on success; non-zero otherwise
145  */
ecryptfs_send_miscdev(char * data,size_t data_size,struct ecryptfs_msg_ctx * msg_ctx,u8 msg_type,u16 msg_flags,struct ecryptfs_daemon * daemon)146 int ecryptfs_send_miscdev(char *data, size_t data_size,
147 			  struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
148 			  u16 msg_flags, struct ecryptfs_daemon *daemon)
149 {
150 	struct ecryptfs_message *msg;
151 
152 	msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
153 	if (!msg)
154 		return -ENOMEM;
155 
156 	mutex_lock(&msg_ctx->mux);
157 	msg_ctx->msg = msg;
158 	msg_ctx->msg->index = msg_ctx->index;
159 	msg_ctx->msg->data_len = data_size;
160 	msg_ctx->type = msg_type;
161 	memcpy(msg_ctx->msg->data, data, data_size);
162 	msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
163 	list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
164 	mutex_unlock(&msg_ctx->mux);
165 
166 	mutex_lock(&daemon->mux);
167 	daemon->num_queued_msg_ctx++;
168 	wake_up_interruptible(&daemon->wait);
169 	mutex_unlock(&daemon->mux);
170 
171 	return 0;
172 }
173 
174 /*
175  * miscdevfs packet format:
176  *  Octet 0: Type
177  *  Octets 1-4: network byte order msg_ctx->counter
178  *  Octets 5-N0: Size of struct ecryptfs_message to follow
179  *  Octets N0-N1: struct ecryptfs_message (including data)
180  *
181  *  Octets 5-N1 not written if the packet type does not include a message
182  */
183 #define PKT_TYPE_SIZE		1
184 #define PKT_CTR_SIZE		4
185 #define MIN_NON_MSG_PKT_SIZE	(PKT_TYPE_SIZE + PKT_CTR_SIZE)
186 #define MIN_MSG_PKT_SIZE	(PKT_TYPE_SIZE + PKT_CTR_SIZE \
187 				 + ECRYPTFS_MIN_PKT_LEN_SIZE)
188 /* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
189 #define MAX_MSG_PKT_SIZE	(PKT_TYPE_SIZE + PKT_CTR_SIZE \
190 				 + ECRYPTFS_MAX_PKT_LEN_SIZE \
191 				 + sizeof(struct ecryptfs_message) \
192 				 + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
193 #define PKT_TYPE_OFFSET		0
194 #define PKT_CTR_OFFSET		PKT_TYPE_SIZE
195 #define PKT_LEN_OFFSET		(PKT_TYPE_SIZE + PKT_CTR_SIZE)
196 
197 /**
198  * ecryptfs_miscdev_read - format and send message from queue
199  * @file: miscdevfs handle
200  * @buf: User buffer into which to copy the next message on the daemon queue
201  * @count: Amount of space available in @buf
202  * @ppos: Offset in file (ignored)
203  *
204  * Pulls the most recent message from the daemon queue, formats it for
205  * being sent via a miscdevfs handle, and copies it into @buf
206  *
207  * Returns the number of bytes copied into the user buffer
208  */
209 static ssize_t
ecryptfs_miscdev_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)210 ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
211 		      loff_t *ppos)
212 {
213 	struct ecryptfs_daemon *daemon = file->private_data;
214 	struct ecryptfs_msg_ctx *msg_ctx;
215 	size_t packet_length_size;
216 	char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
217 	size_t i;
218 	size_t total_length;
219 	int rc;
220 
221 	mutex_lock(&daemon->mux);
222 	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
223 		rc = 0;
224 		printk(KERN_WARNING "%s: Attempt to read from zombified "
225 		       "daemon\n", __func__);
226 		goto out_unlock_daemon;
227 	}
228 	if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
229 		rc = 0;
230 		goto out_unlock_daemon;
231 	}
232 	/* This daemon will not go away so long as this flag is set */
233 	daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
234 check_list:
235 	if (list_empty(&daemon->msg_ctx_out_queue)) {
236 		mutex_unlock(&daemon->mux);
237 		rc = wait_event_interruptible(
238 			daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
239 		mutex_lock(&daemon->mux);
240 		if (rc < 0) {
241 			rc = 0;
242 			goto out_unlock_daemon;
243 		}
244 	}
245 	if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
246 		rc = 0;
247 		goto out_unlock_daemon;
248 	}
249 	if (list_empty(&daemon->msg_ctx_out_queue)) {
250 		/* Something else jumped in since the
251 		 * wait_event_interruptable() and removed the
252 		 * message from the queue; try again */
253 		goto check_list;
254 	}
255 	msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
256 				   struct ecryptfs_msg_ctx, daemon_out_list);
257 	BUG_ON(!msg_ctx);
258 	mutex_lock(&msg_ctx->mux);
259 	if (msg_ctx->msg) {
260 		rc = ecryptfs_write_packet_length(packet_length,
261 						  msg_ctx->msg_size,
262 						  &packet_length_size);
263 		if (rc) {
264 			rc = 0;
265 			printk(KERN_WARNING "%s: Error writing packet length; "
266 			       "rc = [%d]\n", __func__, rc);
267 			goto out_unlock_msg_ctx;
268 		}
269 	} else {
270 		packet_length_size = 0;
271 		msg_ctx->msg_size = 0;
272 	}
273 	total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size
274 			+ msg_ctx->msg_size);
275 	if (count < total_length) {
276 		rc = 0;
277 		printk(KERN_WARNING "%s: Only given user buffer of "
278 		       "size [%zd], but we need [%zd] to read the "
279 		       "pending message\n", __func__, count, total_length);
280 		goto out_unlock_msg_ctx;
281 	}
282 	rc = -EFAULT;
283 	if (put_user(msg_ctx->type, buf))
284 		goto out_unlock_msg_ctx;
285 	if (put_user(cpu_to_be32(msg_ctx->counter),
286 		     (__be32 __user *)(&buf[PKT_CTR_OFFSET])))
287 		goto out_unlock_msg_ctx;
288 	i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
289 	if (msg_ctx->msg) {
290 		if (copy_to_user(&buf[i], packet_length, packet_length_size))
291 			goto out_unlock_msg_ctx;
292 		i += packet_length_size;
293 		if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
294 			goto out_unlock_msg_ctx;
295 		i += msg_ctx->msg_size;
296 	}
297 	rc = i;
298 	list_del(&msg_ctx->daemon_out_list);
299 	kfree(msg_ctx->msg);
300 	msg_ctx->msg = NULL;
301 	/* We do not expect a reply from the userspace daemon for any
302 	 * message type other than ECRYPTFS_MSG_REQUEST */
303 	if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
304 		ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
305 out_unlock_msg_ctx:
306 	mutex_unlock(&msg_ctx->mux);
307 out_unlock_daemon:
308 	daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
309 	mutex_unlock(&daemon->mux);
310 	return rc;
311 }
312 
313 /**
314  * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
315  * @daemon: eCryptfs daemon object
316  * @data: Bytes comprising struct ecryptfs_message
317  * @data_size: sizeof(struct ecryptfs_message) + data len
318  * @seq: Sequence number for miscdev response packet
319  *
320  * Returns zero on success; non-zero otherwise
321  */
ecryptfs_miscdev_response(struct ecryptfs_daemon * daemon,char * data,size_t data_size,u32 seq)322 static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
323 				     size_t data_size, u32 seq)
324 {
325 	struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
326 	int rc;
327 
328 	if ((sizeof(*msg) + msg->data_len) != data_size) {
329 		printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
330 		       "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
331 		       (sizeof(*msg) + msg->data_len), data_size);
332 		rc = -EINVAL;
333 		goto out;
334 	}
335 	rc = ecryptfs_process_response(daemon, msg, seq);
336 	if (rc)
337 		printk(KERN_ERR
338 		       "Error processing response message; rc = [%d]\n", rc);
339 out:
340 	return rc;
341 }
342 
343 /**
344  * ecryptfs_miscdev_write - handle write to daemon miscdev handle
345  * @file: File for misc dev handle
346  * @buf: Buffer containing user data
347  * @count: Amount of data in @buf
348  * @ppos: Pointer to offset in file (ignored)
349  *
350  * Returns the number of bytes read from @buf
351  */
352 static ssize_t
ecryptfs_miscdev_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)353 ecryptfs_miscdev_write(struct file *file, const char __user *buf,
354 		       size_t count, loff_t *ppos)
355 {
356 	__be32 counter_nbo;
357 	u32 seq;
358 	size_t packet_size, packet_size_length;
359 	char *data;
360 	unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
361 	ssize_t rc;
362 
363 	if (count == 0) {
364 		return 0;
365 	} else if (count == MIN_NON_MSG_PKT_SIZE) {
366 		/* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
367 		goto memdup;
368 	} else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
369 		printk(KERN_WARNING "%s: Acceptable packet size range is "
370 		       "[%d-%zu], but amount of data written is [%zu].\n",
371 		       __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
372 		return -EINVAL;
373 	}
374 
375 	if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
376 			   sizeof(packet_size_peek))) {
377 		printk(KERN_WARNING "%s: Error while inspecting packet size\n",
378 		       __func__);
379 		return -EFAULT;
380 	}
381 
382 	rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
383 					  &packet_size_length);
384 	if (rc) {
385 		printk(KERN_WARNING "%s: Error parsing packet length; "
386 		       "rc = [%zd]\n", __func__, rc);
387 		return rc;
388 	}
389 
390 	if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
391 	    != count) {
392 		printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
393 		       packet_size);
394 		return -EINVAL;
395 	}
396 
397 memdup:
398 	data = memdup_user(buf, count);
399 	if (IS_ERR(data)) {
400 		printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
401 		       __func__, PTR_ERR(data));
402 		return PTR_ERR(data);
403 	}
404 	switch (data[PKT_TYPE_OFFSET]) {
405 	case ECRYPTFS_MSG_RESPONSE:
406 		if (count < (MIN_MSG_PKT_SIZE
407 			     + sizeof(struct ecryptfs_message))) {
408 			printk(KERN_WARNING "%s: Minimum acceptable packet "
409 			       "size is [%zd], but amount of data written is "
410 			       "only [%zd]. Discarding response packet.\n",
411 			       __func__,
412 			       (MIN_MSG_PKT_SIZE
413 				+ sizeof(struct ecryptfs_message)), count);
414 			rc = -EINVAL;
415 			goto out_free;
416 		}
417 		memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
418 		seq = be32_to_cpu(counter_nbo);
419 		rc = ecryptfs_miscdev_response(file->private_data,
420 				&data[PKT_LEN_OFFSET + packet_size_length],
421 				packet_size, seq);
422 		if (rc) {
423 			printk(KERN_WARNING "%s: Failed to deliver miscdev "
424 			       "response to requesting operation; rc = [%zd]\n",
425 			       __func__, rc);
426 			goto out_free;
427 		}
428 		break;
429 	case ECRYPTFS_MSG_HELO:
430 	case ECRYPTFS_MSG_QUIT:
431 		break;
432 	default:
433 		ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
434 				"message of unrecognized type [%d]\n",
435 				data[0]);
436 		rc = -EINVAL;
437 		goto out_free;
438 	}
439 	rc = count;
440 out_free:
441 	kfree(data);
442 	return rc;
443 }
444 
445 
446 static const struct file_operations ecryptfs_miscdev_fops = {
447 	.owner   = THIS_MODULE,
448 	.open    = ecryptfs_miscdev_open,
449 	.poll    = ecryptfs_miscdev_poll,
450 	.read    = ecryptfs_miscdev_read,
451 	.write   = ecryptfs_miscdev_write,
452 	.release = ecryptfs_miscdev_release,
453 	.llseek  = noop_llseek,
454 };
455 
456 static struct miscdevice ecryptfs_miscdev = {
457 	.minor = MISC_DYNAMIC_MINOR,
458 	.name  = "ecryptfs",
459 	.fops  = &ecryptfs_miscdev_fops
460 };
461 
462 /**
463  * ecryptfs_init_ecryptfs_miscdev
464  *
465  * Messages sent to the userspace daemon from the kernel are placed on
466  * a queue associated with the daemon. The next read against the
467  * miscdev handle by that daemon will return the oldest message placed
468  * on the message queue for the daemon.
469  *
470  * Returns zero on success; non-zero otherwise
471  */
ecryptfs_init_ecryptfs_miscdev(void)472 int __init ecryptfs_init_ecryptfs_miscdev(void)
473 {
474 	int rc;
475 
476 	atomic_set(&ecryptfs_num_miscdev_opens, 0);
477 	rc = misc_register(&ecryptfs_miscdev);
478 	if (rc)
479 		printk(KERN_ERR "%s: Failed to register miscellaneous device "
480 		       "for communications with userspace daemons; rc = [%d]\n",
481 		       __func__, rc);
482 	return rc;
483 }
484 
485 /**
486  * ecryptfs_destroy_ecryptfs_miscdev
487  *
488  * All of the daemons must be exorcised prior to calling this
489  * function.
490  */
ecryptfs_destroy_ecryptfs_miscdev(void)491 void ecryptfs_destroy_ecryptfs_miscdev(void)
492 {
493 	BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
494 	misc_deregister(&ecryptfs_miscdev);
495 }
496