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Linux/fs/ecryptfs/miscdev.c

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  1 /**
  2  * eCryptfs: Linux filesystem encryption layer
  3  *
  4  * Copyright (C) 2008 International Business Machines Corp.
  5  *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
  6  *
  7  * This program is free software; you can redistribute it and/or
  8  * modify it under the terms of the GNU General Public License version
  9  * 2 as published by the Free Software Foundation.
 10  *
 11  * This program is distributed in the hope that it will be useful, but
 12  * WITHOUT ANY WARRANTY; without even the implied warranty of
 13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 14  * General Public License for more details.
 15  *
 16  * You should have received a copy of the GNU General Public License
 17  * along with this program; if not, write to the Free Software
 18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 19  * 02111-1307, USA.
 20  */
 21 
 22 #include <linux/fs.h>
 23 #include <linux/hash.h>
 24 #include <linux/random.h>
 25 #include <linux/miscdevice.h>
 26 #include <linux/poll.h>
 27 #include <linux/slab.h>
 28 #include <linux/wait.h>
 29 #include <linux/module.h>
 30 #include "ecryptfs_kernel.h"
 31 
 32 static atomic_t ecryptfs_num_miscdev_opens;
 33 
 34 /**
 35  * ecryptfs_miscdev_poll
 36  * @file: dev file
 37  * @pt: dev poll table (ignored)
 38  *
 39  * Returns the poll mask
 40  */
 41 static unsigned int
 42 ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
 43 {
 44         struct ecryptfs_daemon *daemon = file->private_data;
 45         unsigned int mask = 0;
 46 
 47         mutex_lock(&daemon->mux);
 48         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
 49                 printk(KERN_WARNING "%s: Attempt to poll on zombified "
 50                        "daemon\n", __func__);
 51                 goto out_unlock_daemon;
 52         }
 53         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
 54                 goto out_unlock_daemon;
 55         if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
 56                 goto out_unlock_daemon;
 57         daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
 58         mutex_unlock(&daemon->mux);
 59         poll_wait(file, &daemon->wait, pt);
 60         mutex_lock(&daemon->mux);
 61         if (!list_empty(&daemon->msg_ctx_out_queue))
 62                 mask |= POLLIN | POLLRDNORM;
 63 out_unlock_daemon:
 64         daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
 65         mutex_unlock(&daemon->mux);
 66         return mask;
 67 }
 68 
 69 /**
 70  * ecryptfs_miscdev_open
 71  * @inode: inode of miscdev handle (ignored)
 72  * @file: file for miscdev handle
 73  *
 74  * Returns zero on success; non-zero otherwise
 75  */
 76 static int
 77 ecryptfs_miscdev_open(struct inode *inode, struct file *file)
 78 {
 79         struct ecryptfs_daemon *daemon = NULL;
 80         int rc;
 81 
 82         mutex_lock(&ecryptfs_daemon_hash_mux);
 83         rc = ecryptfs_find_daemon_by_euid(&daemon);
 84         if (!rc) {
 85                 rc = -EINVAL;
 86                 goto out_unlock_daemon_list;
 87         }
 88         rc = ecryptfs_spawn_daemon(&daemon, file);
 89         if (rc) {
 90                 printk(KERN_ERR "%s: Error attempting to spawn daemon; "
 91                        "rc = [%d]\n", __func__, rc);
 92                 goto out_unlock_daemon_list;
 93         }
 94         mutex_lock(&daemon->mux);
 95         if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
 96                 rc = -EBUSY;
 97                 goto out_unlock_daemon;
 98         }
 99         daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
100         file->private_data = daemon;
101         atomic_inc(&ecryptfs_num_miscdev_opens);
102 out_unlock_daemon:
103         mutex_unlock(&daemon->mux);
104 out_unlock_daemon_list:
105         mutex_unlock(&ecryptfs_daemon_hash_mux);
106         return rc;
107 }
108 
109 /**
110  * ecryptfs_miscdev_release
111  * @inode: inode of fs/ecryptfs/euid handle (ignored)
112  * @file: file for fs/ecryptfs/euid handle
113  *
114  * This keeps the daemon registered until the daemon sends another
115  * ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
116  *
117  * Returns zero on success; non-zero otherwise
118  */
119 static int
120 ecryptfs_miscdev_release(struct inode *inode, struct file *file)
121 {
122         struct ecryptfs_daemon *daemon = file->private_data;
123         int rc;
124 
125         mutex_lock(&daemon->mux);
126         BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
127         daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
128         atomic_dec(&ecryptfs_num_miscdev_opens);
129         mutex_unlock(&daemon->mux);
130 
131         mutex_lock(&ecryptfs_daemon_hash_mux);
132         rc = ecryptfs_exorcise_daemon(daemon);
133         mutex_unlock(&ecryptfs_daemon_hash_mux);
134         if (rc) {
135                 printk(KERN_CRIT "%s: Fatal error whilst attempting to "
136                        "shut down daemon; rc = [%d]. Please report this "
137                        "bug.\n", __func__, rc);
138                 BUG();
139         }
140         return rc;
141 }
142 
143 /**
144  * ecryptfs_send_miscdev
145  * @data: Data to send to daemon; may be NULL
146  * @data_size: Amount of data to send to daemon
147  * @msg_ctx: Message context, which is used to handle the reply. If
148  *           this is NULL, then we do not expect a reply.
149  * @msg_type: Type of message
150  * @msg_flags: Flags for message
151  * @daemon: eCryptfs daemon object
152  *
153  * Add msg_ctx to queue and then, if it exists, notify the blocked
154  * miscdevess about the data being available. Must be called with
155  * ecryptfs_daemon_hash_mux held.
156  *
157  * Returns zero on success; non-zero otherwise
158  */
159 int ecryptfs_send_miscdev(char *data, size_t data_size,
160                           struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
161                           u16 msg_flags, struct ecryptfs_daemon *daemon)
162 {
163         struct ecryptfs_message *msg;
164 
165         msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
166         if (!msg) {
167                 printk(KERN_ERR "%s: Out of memory whilst attempting "
168                        "to kmalloc(%zd, GFP_KERNEL)\n", __func__,
169                        (sizeof(*msg) + data_size));
170                 return -ENOMEM;
171         }
172 
173         mutex_lock(&msg_ctx->mux);
174         msg_ctx->msg = msg;
175         msg_ctx->msg->index = msg_ctx->index;
176         msg_ctx->msg->data_len = data_size;
177         msg_ctx->type = msg_type;
178         memcpy(msg_ctx->msg->data, data, data_size);
179         msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
180         list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
181         mutex_unlock(&msg_ctx->mux);
182 
183         mutex_lock(&daemon->mux);
184         daemon->num_queued_msg_ctx++;
185         wake_up_interruptible(&daemon->wait);
186         mutex_unlock(&daemon->mux);
187 
188         return 0;
189 }
190 
191 /*
192  * miscdevfs packet format:
193  *  Octet 0: Type
194  *  Octets 1-4: network byte order msg_ctx->counter
195  *  Octets 5-N0: Size of struct ecryptfs_message to follow
196  *  Octets N0-N1: struct ecryptfs_message (including data)
197  *
198  *  Octets 5-N1 not written if the packet type does not include a message
199  */
200 #define PKT_TYPE_SIZE           1
201 #define PKT_CTR_SIZE            4
202 #define MIN_NON_MSG_PKT_SIZE    (PKT_TYPE_SIZE + PKT_CTR_SIZE)
203 #define MIN_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
204                                  + ECRYPTFS_MIN_PKT_LEN_SIZE)
205 /* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
206 #define MAX_MSG_PKT_SIZE        (PKT_TYPE_SIZE + PKT_CTR_SIZE \
207                                  + ECRYPTFS_MAX_PKT_LEN_SIZE \
208                                  + sizeof(struct ecryptfs_message) \
209                                  + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
210 #define PKT_TYPE_OFFSET         0
211 #define PKT_CTR_OFFSET          PKT_TYPE_SIZE
212 #define PKT_LEN_OFFSET          (PKT_TYPE_SIZE + PKT_CTR_SIZE)
213 
214 /**
215  * ecryptfs_miscdev_read - format and send message from queue
216  * @file: miscdevfs handle
217  * @buf: User buffer into which to copy the next message on the daemon queue
218  * @count: Amount of space available in @buf
219  * @ppos: Offset in file (ignored)
220  *
221  * Pulls the most recent message from the daemon queue, formats it for
222  * being sent via a miscdevfs handle, and copies it into @buf
223  *
224  * Returns the number of bytes copied into the user buffer
225  */
226 static ssize_t
227 ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
228                       loff_t *ppos)
229 {
230         struct ecryptfs_daemon *daemon = file->private_data;
231         struct ecryptfs_msg_ctx *msg_ctx;
232         size_t packet_length_size;
233         char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
234         size_t i;
235         size_t total_length;
236         int rc;
237 
238         mutex_lock(&daemon->mux);
239         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
240                 rc = 0;
241                 printk(KERN_WARNING "%s: Attempt to read from zombified "
242                        "daemon\n", __func__);
243                 goto out_unlock_daemon;
244         }
245         if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
246                 rc = 0;
247                 goto out_unlock_daemon;
248         }
249         /* This daemon will not go away so long as this flag is set */
250         daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
251 check_list:
252         if (list_empty(&daemon->msg_ctx_out_queue)) {
253                 mutex_unlock(&daemon->mux);
254                 rc = wait_event_interruptible(
255                         daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
256                 mutex_lock(&daemon->mux);
257                 if (rc < 0) {
258                         rc = 0;
259                         goto out_unlock_daemon;
260                 }
261         }
262         if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
263                 rc = 0;
264                 goto out_unlock_daemon;
265         }
266         if (list_empty(&daemon->msg_ctx_out_queue)) {
267                 /* Something else jumped in since the
268                  * wait_event_interruptable() and removed the
269                  * message from the queue; try again */
270                 goto check_list;
271         }
272         msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
273                                    struct ecryptfs_msg_ctx, daemon_out_list);
274         BUG_ON(!msg_ctx);
275         mutex_lock(&msg_ctx->mux);
276         if (msg_ctx->msg) {
277                 rc = ecryptfs_write_packet_length(packet_length,
278                                                   msg_ctx->msg_size,
279                                                   &packet_length_size);
280                 if (rc) {
281                         rc = 0;
282                         printk(KERN_WARNING "%s: Error writing packet length; "
283                                "rc = [%d]\n", __func__, rc);
284                         goto out_unlock_msg_ctx;
285                 }
286         } else {
287                 packet_length_size = 0;
288                 msg_ctx->msg_size = 0;
289         }
290         total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size
291                         + msg_ctx->msg_size);
292         if (count < total_length) {
293                 rc = 0;
294                 printk(KERN_WARNING "%s: Only given user buffer of "
295                        "size [%zd], but we need [%zd] to read the "
296                        "pending message\n", __func__, count, total_length);
297                 goto out_unlock_msg_ctx;
298         }
299         rc = -EFAULT;
300         if (put_user(msg_ctx->type, buf))
301                 goto out_unlock_msg_ctx;
302         if (put_user(cpu_to_be32(msg_ctx->counter),
303                      (__be32 __user *)(&buf[PKT_CTR_OFFSET])))
304                 goto out_unlock_msg_ctx;
305         i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
306         if (msg_ctx->msg) {
307                 if (copy_to_user(&buf[i], packet_length, packet_length_size))
308                         goto out_unlock_msg_ctx;
309                 i += packet_length_size;
310                 if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
311                         goto out_unlock_msg_ctx;
312                 i += msg_ctx->msg_size;
313         }
314         rc = i;
315         list_del(&msg_ctx->daemon_out_list);
316         kfree(msg_ctx->msg);
317         msg_ctx->msg = NULL;
318         /* We do not expect a reply from the userspace daemon for any
319          * message type other than ECRYPTFS_MSG_REQUEST */
320         if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
321                 ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
322 out_unlock_msg_ctx:
323         mutex_unlock(&msg_ctx->mux);
324 out_unlock_daemon:
325         daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
326         mutex_unlock(&daemon->mux);
327         return rc;
328 }
329 
330 /**
331  * ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
332  * @data: Bytes comprising struct ecryptfs_message
333  * @data_size: sizeof(struct ecryptfs_message) + data len
334  * @seq: Sequence number for miscdev response packet
335  *
336  * Returns zero on success; non-zero otherwise
337  */
338 static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
339                                      size_t data_size, u32 seq)
340 {
341         struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
342         int rc;
343 
344         if ((sizeof(*msg) + msg->data_len) != data_size) {
345                 printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
346                        "[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
347                        (sizeof(*msg) + msg->data_len), data_size);
348                 rc = -EINVAL;
349                 goto out;
350         }
351         rc = ecryptfs_process_response(daemon, msg, seq);
352         if (rc)
353                 printk(KERN_ERR
354                        "Error processing response message; rc = [%d]\n", rc);
355 out:
356         return rc;
357 }
358 
359 /**
360  * ecryptfs_miscdev_write - handle write to daemon miscdev handle
361  * @file: File for misc dev handle
362  * @buf: Buffer containing user data
363  * @count: Amount of data in @buf
364  * @ppos: Pointer to offset in file (ignored)
365  *
366  * Returns the number of bytes read from @buf
367  */
368 static ssize_t
369 ecryptfs_miscdev_write(struct file *file, const char __user *buf,
370                        size_t count, loff_t *ppos)
371 {
372         __be32 counter_nbo;
373         u32 seq;
374         size_t packet_size, packet_size_length;
375         char *data;
376         unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
377         ssize_t rc;
378 
379         if (count == 0) {
380                 return 0;
381         } else if (count == MIN_NON_MSG_PKT_SIZE) {
382                 /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
383                 goto memdup;
384         } else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
385                 printk(KERN_WARNING "%s: Acceptable packet size range is "
386                        "[%d-%zu], but amount of data written is [%zu].",
387                        __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
388                 return -EINVAL;
389         }
390 
391         if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
392                            sizeof(packet_size_peek))) {
393                 printk(KERN_WARNING "%s: Error while inspecting packet size\n",
394                        __func__);
395                 return -EFAULT;
396         }
397 
398         rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
399                                           &packet_size_length);
400         if (rc) {
401                 printk(KERN_WARNING "%s: Error parsing packet length; "
402                        "rc = [%zd]\n", __func__, rc);
403                 return rc;
404         }
405 
406         if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
407             != count) {
408                 printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
409                        packet_size);
410                 return -EINVAL;
411         }
412 
413 memdup:
414         data = memdup_user(buf, count);
415         if (IS_ERR(data)) {
416                 printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
417                        __func__, PTR_ERR(data));
418                 return PTR_ERR(data);
419         }
420         switch (data[PKT_TYPE_OFFSET]) {
421         case ECRYPTFS_MSG_RESPONSE:
422                 if (count < (MIN_MSG_PKT_SIZE
423                              + sizeof(struct ecryptfs_message))) {
424                         printk(KERN_WARNING "%s: Minimum acceptable packet "
425                                "size is [%zd], but amount of data written is "
426                                "only [%zd]. Discarding response packet.\n",
427                                __func__,
428                                (MIN_MSG_PKT_SIZE
429                                 + sizeof(struct ecryptfs_message)), count);
430                         rc = -EINVAL;
431                         goto out_free;
432                 }
433                 memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
434                 seq = be32_to_cpu(counter_nbo);
435                 rc = ecryptfs_miscdev_response(file->private_data,
436                                 &data[PKT_LEN_OFFSET + packet_size_length],
437                                 packet_size, seq);
438                 if (rc) {
439                         printk(KERN_WARNING "%s: Failed to deliver miscdev "
440                                "response to requesting operation; rc = [%zd]\n",
441                                __func__, rc);
442                         goto out_free;
443                 }
444                 break;
445         case ECRYPTFS_MSG_HELO:
446         case ECRYPTFS_MSG_QUIT:
447                 break;
448         default:
449                 ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
450                                 "message of unrecognized type [%d]\n",
451                                 data[0]);
452                 rc = -EINVAL;
453                 goto out_free;
454         }
455         rc = count;
456 out_free:
457         kfree(data);
458         return rc;
459 }
460 
461 
462 static const struct file_operations ecryptfs_miscdev_fops = {
463         .owner   = THIS_MODULE,
464         .open    = ecryptfs_miscdev_open,
465         .poll    = ecryptfs_miscdev_poll,
466         .read    = ecryptfs_miscdev_read,
467         .write   = ecryptfs_miscdev_write,
468         .release = ecryptfs_miscdev_release,
469         .llseek  = noop_llseek,
470 };
471 
472 static struct miscdevice ecryptfs_miscdev = {
473         .minor = MISC_DYNAMIC_MINOR,
474         .name  = "ecryptfs",
475         .fops  = &ecryptfs_miscdev_fops
476 };
477 
478 /**
479  * ecryptfs_init_ecryptfs_miscdev
480  *
481  * Messages sent to the userspace daemon from the kernel are placed on
482  * a queue associated with the daemon. The next read against the
483  * miscdev handle by that daemon will return the oldest message placed
484  * on the message queue for the daemon.
485  *
486  * Returns zero on success; non-zero otherwise
487  */
488 int __init ecryptfs_init_ecryptfs_miscdev(void)
489 {
490         int rc;
491 
492         atomic_set(&ecryptfs_num_miscdev_opens, 0);
493         rc = misc_register(&ecryptfs_miscdev);
494         if (rc)
495                 printk(KERN_ERR "%s: Failed to register miscellaneous device "
496                        "for communications with userspace daemons; rc = [%d]\n",
497                        __func__, rc);
498         return rc;
499 }
500 
501 /**
502  * ecryptfs_destroy_ecryptfs_miscdev
503  *
504  * All of the daemons must be exorcised prior to calling this
505  * function.
506  */
507 void ecryptfs_destroy_ecryptfs_miscdev(void)
508 {
509         BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
510         misc_deregister(&ecryptfs_miscdev);
511 }
512 

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