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