ecryptfs: Fix warning in ecryptfs_process_response()
[linux-2.6.git] / fs / ecryptfs / mmap.c
1 /**
2  * eCryptfs: Linux filesystem encryption layer
3  * This is where eCryptfs coordinates the symmetric encryption and
4  * decryption of the file data as it passes between the lower
5  * encrypted file and the upper decrypted file.
6  *
7  * Copyright (C) 1997-2003 Erez Zadok
8  * Copyright (C) 2001-2003 Stony Brook University
9  * Copyright (C) 2004-2007 International Business Machines Corp.
10  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
11  *
12  * This program is free software; you can redistribute it and/or
13  * modify it under the terms of the GNU General Public License as
14  * published by the Free Software Foundation; either version 2 of the
15  * License, or (at your option) any later version.
16  *
17  * This program is distributed in the hope that it will be useful, but
18  * WITHOUT ANY WARRANTY; without even the implied warranty of
19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
20  * General Public License for more details.
21  *
22  * You should have received a copy of the GNU General Public License
23  * along with this program; if not, write to the Free Software
24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
25  * 02111-1307, USA.
26  */
27
28 #include <linux/pagemap.h>
29 #include <linux/writeback.h>
30 #include <linux/page-flags.h>
31 #include <linux/mount.h>
32 #include <linux/file.h>
33 #include <linux/crypto.h>
34 #include <linux/scatterlist.h>
35 #include <linux/slab.h>
36 #include <asm/unaligned.h>
37 #include "ecryptfs_kernel.h"
38
39 /**
40  * ecryptfs_get_locked_page
41  *
42  * Get one page from cache or lower f/s, return error otherwise.
43  *
44  * Returns locked and up-to-date page (if ok), with increased
45  * refcnt.
46  */
47 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
48 {
49         struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
50         if (!IS_ERR(page))
51                 lock_page(page);
52         return page;
53 }
54
55 /**
56  * ecryptfs_writepage
57  * @page: Page that is locked before this call is made
58  *
59  * Returns zero on success; non-zero otherwise
60  */
61 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
62 {
63         int rc;
64
65         rc = ecryptfs_encrypt_page(page);
66         if (rc) {
67                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
68                                 "page (upper index [0x%.16x])\n", page->index);
69                 ClearPageUptodate(page);
70                 goto out;
71         }
72         SetPageUptodate(page);
73         unlock_page(page);
74 out:
75         return rc;
76 }
77
78 static void strip_xattr_flag(char *page_virt,
79                              struct ecryptfs_crypt_stat *crypt_stat)
80 {
81         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
82                 size_t written;
83
84                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
85                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
86                                                 &written);
87                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
88         }
89 }
90
91 /**
92  *   Header Extent:
93  *     Octets 0-7:        Unencrypted file size (big-endian)
94  *     Octets 8-15:       eCryptfs special marker
95  *     Octets 16-19:      Flags
96  *      Octet 16:         File format version number (between 0 and 255)
97  *      Octets 17-18:     Reserved
98  *      Octet 19:         Bit 1 (lsb): Reserved
99  *                        Bit 2: Encrypted?
100  *                        Bits 3-8: Reserved
101  *     Octets 20-23:      Header extent size (big-endian)
102  *     Octets 24-25:      Number of header extents at front of file
103  *                        (big-endian)
104  *     Octet  26:         Begin RFC 2440 authentication token packet set
105  */
106
107 /**
108  * ecryptfs_copy_up_encrypted_with_header
109  * @page: Sort of a ``virtual'' representation of the encrypted lower
110  *        file. The actual lower file does not have the metadata in
111  *        the header. This is locked.
112  * @crypt_stat: The eCryptfs inode's cryptographic context
113  *
114  * The ``view'' is the version of the file that userspace winds up
115  * seeing, with the header information inserted.
116  */
117 static int
118 ecryptfs_copy_up_encrypted_with_header(struct page *page,
119                                        struct ecryptfs_crypt_stat *crypt_stat)
120 {
121         loff_t extent_num_in_page = 0;
122         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
123                                        / crypt_stat->extent_size);
124         int rc = 0;
125
126         while (extent_num_in_page < num_extents_per_page) {
127                 loff_t view_extent_num = ((((loff_t)page->index)
128                                            * num_extents_per_page)
129                                           + extent_num_in_page);
130                 size_t num_header_extents_at_front =
131                         (crypt_stat->metadata_size / crypt_stat->extent_size);
132
133                 if (view_extent_num < num_header_extents_at_front) {
134                         /* This is a header extent */
135                         char *page_virt;
136
137                         page_virt = kmap_atomic(page, KM_USER0);
138                         memset(page_virt, 0, PAGE_CACHE_SIZE);
139                         /* TODO: Support more than one header extent */
140                         if (view_extent_num == 0) {
141                                 size_t written;
142
143                                 rc = ecryptfs_read_xattr_region(
144                                         page_virt, page->mapping->host);
145                                 strip_xattr_flag(page_virt + 16, crypt_stat);
146                                 ecryptfs_write_header_metadata(page_virt + 20,
147                                                                crypt_stat,
148                                                                &written);
149                         }
150                         kunmap_atomic(page_virt, KM_USER0);
151                         flush_dcache_page(page);
152                         if (rc) {
153                                 printk(KERN_ERR "%s: Error reading xattr "
154                                        "region; rc = [%d]\n", __func__, rc);
155                                 goto out;
156                         }
157                 } else {
158                         /* This is an encrypted data extent */
159                         loff_t lower_offset =
160                                 ((view_extent_num * crypt_stat->extent_size)
161                                  - crypt_stat->metadata_size);
162
163                         rc = ecryptfs_read_lower_page_segment(
164                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
165                                 (lower_offset & ~PAGE_CACHE_MASK),
166                                 crypt_stat->extent_size, page->mapping->host);
167                         if (rc) {
168                                 printk(KERN_ERR "%s: Error attempting to read "
169                                        "extent at offset [%lld] in the lower "
170                                        "file; rc = [%d]\n", __func__,
171                                        lower_offset, rc);
172                                 goto out;
173                         }
174                 }
175                 extent_num_in_page++;
176         }
177 out:
178         return rc;
179 }
180
181 /**
182  * ecryptfs_readpage
183  * @file: An eCryptfs file
184  * @page: Page from eCryptfs inode mapping into which to stick the read data
185  *
186  * Read in a page, decrypting if necessary.
187  *
188  * Returns zero on success; non-zero on error.
189  */
190 static int ecryptfs_readpage(struct file *file, struct page *page)
191 {
192         struct ecryptfs_crypt_stat *crypt_stat =
193                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
194         int rc = 0;
195
196         if (!crypt_stat
197             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
198             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
199                 ecryptfs_printk(KERN_DEBUG,
200                                 "Passing through unencrypted page\n");
201                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
202                                                       PAGE_CACHE_SIZE,
203                                                       page->mapping->host);
204         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
205                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
206                         rc = ecryptfs_copy_up_encrypted_with_header(page,
207                                                                     crypt_stat);
208                         if (rc) {
209                                 printk(KERN_ERR "%s: Error attempting to copy "
210                                        "the encrypted content from the lower "
211                                        "file whilst inserting the metadata "
212                                        "from the xattr into the header; rc = "
213                                        "[%d]\n", __func__, rc);
214                                 goto out;
215                         }
216
217                 } else {
218                         rc = ecryptfs_read_lower_page_segment(
219                                 page, page->index, 0, PAGE_CACHE_SIZE,
220                                 page->mapping->host);
221                         if (rc) {
222                                 printk(KERN_ERR "Error reading page; rc = "
223                                        "[%d]\n", rc);
224                                 goto out;
225                         }
226                 }
227         } else {
228                 rc = ecryptfs_decrypt_page(page);
229                 if (rc) {
230                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
231                                         "rc = [%d]\n", rc);
232                         goto out;
233                 }
234         }
235 out:
236         if (rc)
237                 ClearPageUptodate(page);
238         else
239                 SetPageUptodate(page);
240         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
241                         page->index);
242         unlock_page(page);
243         return rc;
244 }
245
246 /**
247  * Called with lower inode mutex held.
248  */
249 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
250 {
251         struct inode *inode = page->mapping->host;
252         int end_byte_in_page;
253
254         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
255                 goto out;
256         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
257         if (to > end_byte_in_page)
258                 end_byte_in_page = to;
259         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
260 out:
261         return 0;
262 }
263
264 /**
265  * ecryptfs_write_begin
266  * @file: The eCryptfs file
267  * @mapping: The eCryptfs object
268  * @pos: The file offset at which to start writing
269  * @len: Length of the write
270  * @flags: Various flags
271  * @pagep: Pointer to return the page
272  * @fsdata: Pointer to return fs data (unused)
273  *
274  * This function must zero any hole we create
275  *
276  * Returns zero on success; non-zero otherwise
277  */
278 static int ecryptfs_write_begin(struct file *file,
279                         struct address_space *mapping,
280                         loff_t pos, unsigned len, unsigned flags,
281                         struct page **pagep, void **fsdata)
282 {
283         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
284         struct page *page;
285         loff_t prev_page_end_size;
286         int rc = 0;
287
288         page = grab_cache_page_write_begin(mapping, index, flags);
289         if (!page)
290                 return -ENOMEM;
291         *pagep = page;
292
293         if (!PageUptodate(page)) {
294                 struct ecryptfs_crypt_stat *crypt_stat =
295                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
296
297                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
298                     || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
299                         rc = ecryptfs_read_lower_page_segment(
300                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
301                         if (rc) {
302                                 printk(KERN_ERR "%s: Error attemping to read "
303                                        "lower page segment; rc = [%d]\n",
304                                        __func__, rc);
305                                 ClearPageUptodate(page);
306                                 goto out;
307                         } else
308                                 SetPageUptodate(page);
309                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
310                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
311                                 rc = ecryptfs_copy_up_encrypted_with_header(
312                                         page, crypt_stat);
313                                 if (rc) {
314                                         printk(KERN_ERR "%s: Error attempting "
315                                                "to copy the encrypted content "
316                                                "from the lower file whilst "
317                                                "inserting the metadata from "
318                                                "the xattr into the header; rc "
319                                                "= [%d]\n", __func__, rc);
320                                         ClearPageUptodate(page);
321                                         goto out;
322                                 }
323                                 SetPageUptodate(page);
324                         } else {
325                                 rc = ecryptfs_read_lower_page_segment(
326                                         page, index, 0, PAGE_CACHE_SIZE,
327                                         mapping->host);
328                                 if (rc) {
329                                         printk(KERN_ERR "%s: Error reading "
330                                                "page; rc = [%d]\n",
331                                                __func__, rc);
332                                         ClearPageUptodate(page);
333                                         goto out;
334                                 }
335                                 SetPageUptodate(page);
336                         }
337                 } else {
338                         rc = ecryptfs_decrypt_page(page);
339                         if (rc) {
340                                 printk(KERN_ERR "%s: Error decrypting page "
341                                        "at index [%ld]; rc = [%d]\n",
342                                        __func__, page->index, rc);
343                                 ClearPageUptodate(page);
344                                 goto out;
345                         }
346                         SetPageUptodate(page);
347                 }
348         }
349         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
350         /* If creating a page or more of holes, zero them out via truncate.
351          * Note, this will increase i_size. */
352         if (index != 0) {
353                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
354                         rc = ecryptfs_truncate(file->f_path.dentry,
355                                                prev_page_end_size);
356                         if (rc) {
357                                 printk(KERN_ERR "%s: Error on attempt to "
358                                        "truncate to (higher) offset [%lld];"
359                                        " rc = [%d]\n", __func__,
360                                        prev_page_end_size, rc);
361                                 goto out;
362                         }
363                 }
364         }
365         /* Writing to a new page, and creating a small hole from start
366          * of page?  Zero it out. */
367         if ((i_size_read(mapping->host) == prev_page_end_size)
368             && (pos != 0))
369                 zero_user(page, 0, PAGE_CACHE_SIZE);
370 out:
371         return rc;
372 }
373
374 /**
375  * ecryptfs_write_inode_size_to_header
376  *
377  * Writes the lower file size to the first 8 bytes of the header.
378  *
379  * Returns zero on success; non-zero on error.
380  */
381 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
382 {
383         char *file_size_virt;
384         int rc;
385
386         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
387         if (!file_size_virt) {
388                 rc = -ENOMEM;
389                 goto out;
390         }
391         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
392         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
393                                   sizeof(u64));
394         kfree(file_size_virt);
395         if (rc < 0)
396                 printk(KERN_ERR "%s: Error writing file size to header; "
397                        "rc = [%d]\n", __func__, rc);
398         else
399                 rc = 0;
400 out:
401         return rc;
402 }
403
404 struct kmem_cache *ecryptfs_xattr_cache;
405
406 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
407 {
408         ssize_t size;
409         void *xattr_virt;
410         struct dentry *lower_dentry =
411                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
412         struct inode *lower_inode = lower_dentry->d_inode;
413         int rc;
414
415         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
416                 printk(KERN_WARNING
417                        "No support for setting xattr in lower filesystem\n");
418                 rc = -ENOSYS;
419                 goto out;
420         }
421         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
422         if (!xattr_virt) {
423                 printk(KERN_ERR "Out of memory whilst attempting to write "
424                        "inode size to xattr\n");
425                 rc = -ENOMEM;
426                 goto out;
427         }
428         mutex_lock(&lower_inode->i_mutex);
429         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
430                                            xattr_virt, PAGE_CACHE_SIZE);
431         if (size < 0)
432                 size = 8;
433         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
434         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
435                                          xattr_virt, size, 0);
436         mutex_unlock(&lower_inode->i_mutex);
437         if (rc)
438                 printk(KERN_ERR "Error whilst attempting to write inode size "
439                        "to lower file xattr; rc = [%d]\n", rc);
440         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
441 out:
442         return rc;
443 }
444
445 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
446 {
447         struct ecryptfs_crypt_stat *crypt_stat;
448
449         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
450         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
451         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
452                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
453         else
454                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
455 }
456
457 /**
458  * ecryptfs_write_end
459  * @file: The eCryptfs file object
460  * @mapping: The eCryptfs object
461  * @pos: The file position
462  * @len: The length of the data (unused)
463  * @copied: The amount of data copied
464  * @page: The eCryptfs page
465  * @fsdata: The fsdata (unused)
466  *
467  * This is where we encrypt the data and pass the encrypted data to
468  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
469  * entire underlying packets.
470  */
471 static int ecryptfs_write_end(struct file *file,
472                         struct address_space *mapping,
473                         loff_t pos, unsigned len, unsigned copied,
474                         struct page *page, void *fsdata)
475 {
476         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
477         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
478         unsigned to = from + copied;
479         struct inode *ecryptfs_inode = mapping->host;
480         struct ecryptfs_crypt_stat *crypt_stat =
481                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
482         int rc;
483
484         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
485                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
486                         "crypt_stat at memory location [%p]\n", crypt_stat);
487                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
488         } else
489                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
490         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
491                         "(page w/ index = [0x%.16x], to = [%d])\n", index, to);
492         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
493                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
494                                                        to);
495                 if (!rc) {
496                         rc = copied;
497                         fsstack_copy_inode_size(ecryptfs_inode,
498                                 ecryptfs_inode_to_lower(ecryptfs_inode));
499                 }
500                 goto out;
501         }
502         /* Fills in zeros if 'to' goes beyond inode size */
503         rc = fill_zeros_to_end_of_page(page, to);
504         if (rc) {
505                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
506                         "zeros in page with index = [0x%.16x]\n", index);
507                 goto out;
508         }
509         rc = ecryptfs_encrypt_page(page);
510         if (rc) {
511                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
512                                 "index [0x%.16x])\n", index);
513                 goto out;
514         }
515         if (pos + copied > i_size_read(ecryptfs_inode)) {
516                 i_size_write(ecryptfs_inode, pos + copied);
517                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
518                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
519         }
520         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
521         if (rc)
522                 printk(KERN_ERR "Error writing inode size to metadata; "
523                        "rc = [%d]\n", rc);
524         else
525                 rc = copied;
526 out:
527         unlock_page(page);
528         page_cache_release(page);
529         return rc;
530 }
531
532 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
533 {
534         int rc = 0;
535         struct inode *inode;
536         struct inode *lower_inode;
537
538         inode = (struct inode *)mapping->host;
539         lower_inode = ecryptfs_inode_to_lower(inode);
540         if (lower_inode->i_mapping->a_ops->bmap)
541                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
542                                                          block);
543         return rc;
544 }
545
546 const struct address_space_operations ecryptfs_aops = {
547         .writepage = ecryptfs_writepage,
548         .readpage = ecryptfs_readpage,
549         .write_begin = ecryptfs_write_begin,
550         .write_end = ecryptfs_write_end,
551         .bmap = ecryptfs_bmap,
552 };