Merge git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-x86
[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 "ecryptfs_kernel.h"
36
37 /**
38  * ecryptfs_get_locked_page
39  *
40  * Get one page from cache or lower f/s, return error otherwise.
41  *
42  * Returns locked and up-to-date page (if ok), with increased
43  * refcnt.
44  */
45 struct page *ecryptfs_get_locked_page(struct file *file, loff_t index)
46 {
47         struct dentry *dentry;
48         struct inode *inode;
49         struct address_space *mapping;
50         struct page *page;
51
52         dentry = file->f_path.dentry;
53         inode = dentry->d_inode;
54         mapping = inode->i_mapping;
55         page = read_mapping_page(mapping, index, (void *)file);
56         if (!IS_ERR(page))
57                 lock_page(page);
58         return page;
59 }
60
61 /**
62  * ecryptfs_writepage
63  * @page: Page that is locked before this call is made
64  *
65  * Returns zero on success; non-zero otherwise
66  */
67 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
68 {
69         int rc;
70
71         rc = ecryptfs_encrypt_page(page);
72         if (rc) {
73                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
74                                 "page (upper index [0x%.16x])\n", page->index);
75                 ClearPageUptodate(page);
76                 goto out;
77         }
78         SetPageUptodate(page);
79         unlock_page(page);
80 out:
81         return rc;
82 }
83
84 /**
85  *   Header Extent:
86  *     Octets 0-7:        Unencrypted file size (big-endian)
87  *     Octets 8-15:       eCryptfs special marker
88  *     Octets 16-19:      Flags
89  *      Octet 16:         File format version number (between 0 and 255)
90  *      Octets 17-18:     Reserved
91  *      Octet 19:         Bit 1 (lsb): Reserved
92  *                        Bit 2: Encrypted?
93  *                        Bits 3-8: Reserved
94  *     Octets 20-23:      Header extent size (big-endian)
95  *     Octets 24-25:      Number of header extents at front of file
96  *                        (big-endian)
97  *     Octet  26:         Begin RFC 2440 authentication token packet set
98  */
99 static void set_header_info(char *page_virt,
100                             struct ecryptfs_crypt_stat *crypt_stat)
101 {
102         size_t written;
103         size_t save_num_header_bytes_at_front =
104                 crypt_stat->num_header_bytes_at_front;
105
106         crypt_stat->num_header_bytes_at_front =
107                 ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
108         ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
109         crypt_stat->num_header_bytes_at_front =
110                 save_num_header_bytes_at_front;
111 }
112
113 /**
114  * ecryptfs_copy_up_encrypted_with_header
115  * @page: Sort of a ``virtual'' representation of the encrypted lower
116  *        file. The actual lower file does not have the metadata in
117  *        the header. This is locked.
118  * @crypt_stat: The eCryptfs inode's cryptographic context
119  *
120  * The ``view'' is the version of the file that userspace winds up
121  * seeing, with the header information inserted.
122  */
123 static int
124 ecryptfs_copy_up_encrypted_with_header(struct page *page,
125                                        struct ecryptfs_crypt_stat *crypt_stat)
126 {
127         loff_t extent_num_in_page = 0;
128         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
129                                        / crypt_stat->extent_size);
130         int rc = 0;
131
132         while (extent_num_in_page < num_extents_per_page) {
133                 loff_t view_extent_num = ((((loff_t)page->index)
134                                            * num_extents_per_page)
135                                           + extent_num_in_page);
136                 size_t num_header_extents_at_front =
137                         (crypt_stat->num_header_bytes_at_front
138                          / crypt_stat->extent_size);
139
140                 if (view_extent_num < num_header_extents_at_front) {
141                         /* This is a header extent */
142                         char *page_virt;
143
144                         page_virt = kmap_atomic(page, KM_USER0);
145                         memset(page_virt, 0, PAGE_CACHE_SIZE);
146                         /* TODO: Support more than one header extent */
147                         if (view_extent_num == 0) {
148                                 rc = ecryptfs_read_xattr_region(
149                                         page_virt, page->mapping->host);
150                                 set_header_info(page_virt, crypt_stat);
151                         }
152                         kunmap_atomic(page_virt, KM_USER0);
153                         flush_dcache_page(page);
154                         if (rc) {
155                                 printk(KERN_ERR "%s: Error reading xattr "
156                                        "region; rc = [%d]\n", __FUNCTION__, rc);
157                                 goto out;
158                         }
159                 } else {
160                         /* This is an encrypted data extent */
161                         loff_t lower_offset =
162                                 ((view_extent_num * crypt_stat->extent_size)
163                                  - crypt_stat->num_header_bytes_at_front);
164
165                         rc = ecryptfs_read_lower_page_segment(
166                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
167                                 (lower_offset & ~PAGE_CACHE_MASK),
168                                 crypt_stat->extent_size, page->mapping->host);
169                         if (rc) {
170                                 printk(KERN_ERR "%s: Error attempting to read "
171                                        "extent at offset [%lld] in the lower "
172                                        "file; rc = [%d]\n", __FUNCTION__,
173                                        lower_offset, rc);
174                                 goto out;
175                         }
176                 }
177                 extent_num_in_page++;
178         }
179 out:
180         return rc;
181 }
182
183 /**
184  * ecryptfs_readpage
185  * @file: An eCryptfs file
186  * @page: Page from eCryptfs inode mapping into which to stick the read data
187  *
188  * Read in a page, decrypting if necessary.
189  *
190  * Returns zero on success; non-zero on error.
191  */
192 static int ecryptfs_readpage(struct file *file, struct page *page)
193 {
194         struct ecryptfs_crypt_stat *crypt_stat =
195                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
196         int rc = 0;
197
198         if (!crypt_stat
199             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
200             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
201                 ecryptfs_printk(KERN_DEBUG,
202                                 "Passing through unencrypted page\n");
203                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
204                                                       PAGE_CACHE_SIZE,
205                                                       page->mapping->host);
206         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
207                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
208                         rc = ecryptfs_copy_up_encrypted_with_header(page,
209                                                                     crypt_stat);
210                         if (rc) {
211                                 printk(KERN_ERR "%s: Error attempting to copy "
212                                        "the encrypted content from the lower "
213                                        "file whilst inserting the metadata "
214                                        "from the xattr into the header; rc = "
215                                        "[%d]\n", __FUNCTION__, rc);
216                                 goto out;
217                         }
218
219                 } else {
220                         rc = ecryptfs_read_lower_page_segment(
221                                 page, page->index, 0, PAGE_CACHE_SIZE,
222                                 page->mapping->host);
223                         if (rc) {
224                                 printk(KERN_ERR "Error reading page; rc = "
225                                        "[%d]\n", rc);
226                                 goto out;
227                         }
228                 }
229         } else {
230                 rc = ecryptfs_decrypt_page(page);
231                 if (rc) {
232                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
233                                         "rc = [%d]\n", rc);
234                         goto out;
235                 }
236         }
237 out:
238         if (rc)
239                 ClearPageUptodate(page);
240         else
241                 SetPageUptodate(page);
242         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
243                         page->index);
244         unlock_page(page);
245         return rc;
246 }
247
248 /**
249  * Called with lower inode mutex held.
250  */
251 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
252 {
253         struct inode *inode = page->mapping->host;
254         int end_byte_in_page;
255
256         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
257                 goto out;
258         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
259         if (to > end_byte_in_page)
260                 end_byte_in_page = to;
261         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
262 out:
263         return 0;
264 }
265
266 /* This function must zero any hole we create */
267 static int ecryptfs_prepare_write(struct file *file, struct page *page,
268                                   unsigned from, unsigned to)
269 {
270         int rc = 0;
271         loff_t prev_page_end_size;
272
273         if (!PageUptodate(page)) {
274                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
275                                                       PAGE_CACHE_SIZE,
276                                                       page->mapping->host);
277                 if (rc) {
278                         printk(KERN_ERR "%s: Error attemping to read lower "
279                                "page segment; rc = [%d]\n", __FUNCTION__, rc);
280                         ClearPageUptodate(page);
281                         goto out;
282                 } else
283                         SetPageUptodate(page);
284         }
285
286         prev_page_end_size = ((loff_t)page->index << PAGE_CACHE_SHIFT);
287
288         /*
289          * If creating a page or more of holes, zero them out via truncate.
290          * Note, this will increase i_size.
291          */
292         if (page->index != 0) {
293                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
294                         rc = ecryptfs_truncate(file->f_path.dentry,
295                                                prev_page_end_size);
296                         if (rc) {
297                                 printk(KERN_ERR "Error on attempt to "
298                                        "truncate to (higher) offset [%lld];"
299                                        " rc = [%d]\n", prev_page_end_size, rc);
300                                 goto out;
301                         }
302                 }
303         }
304         /*
305          * Writing to a new page, and creating a small hole from start of page?
306          * Zero it out.
307          */
308         if ((i_size_read(page->mapping->host) == prev_page_end_size) &&
309             (from != 0)) {
310                 zero_user(page, 0, PAGE_CACHE_SIZE);
311         }
312 out:
313         return rc;
314 }
315
316 /**
317  * ecryptfs_write_inode_size_to_header
318  *
319  * Writes the lower file size to the first 8 bytes of the header.
320  *
321  * Returns zero on success; non-zero on error.
322  */
323 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
324 {
325         u64 file_size;
326         char *file_size_virt;
327         int rc;
328
329         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
330         if (!file_size_virt) {
331                 rc = -ENOMEM;
332                 goto out;
333         }
334         file_size = (u64)i_size_read(ecryptfs_inode);
335         file_size = cpu_to_be64(file_size);
336         memcpy(file_size_virt, &file_size, sizeof(u64));
337         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
338                                   sizeof(u64));
339         kfree(file_size_virt);
340         if (rc)
341                 printk(KERN_ERR "%s: Error writing file size to header; "
342                        "rc = [%d]\n", __FUNCTION__, rc);
343 out:
344         return rc;
345 }
346
347 struct kmem_cache *ecryptfs_xattr_cache;
348
349 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
350 {
351         ssize_t size;
352         void *xattr_virt;
353         struct dentry *lower_dentry =
354                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
355         struct inode *lower_inode = lower_dentry->d_inode;
356         u64 file_size;
357         int rc;
358
359         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
360                 printk(KERN_WARNING
361                        "No support for setting xattr in lower filesystem\n");
362                 rc = -ENOSYS;
363                 goto out;
364         }
365         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
366         if (!xattr_virt) {
367                 printk(KERN_ERR "Out of memory whilst attempting to write "
368                        "inode size to xattr\n");
369                 rc = -ENOMEM;
370                 goto out;
371         }
372         mutex_lock(&lower_inode->i_mutex);
373         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
374                                            xattr_virt, PAGE_CACHE_SIZE);
375         if (size < 0)
376                 size = 8;
377         file_size = (u64)i_size_read(ecryptfs_inode);
378         file_size = cpu_to_be64(file_size);
379         memcpy(xattr_virt, &file_size, sizeof(u64));
380         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
381                                          xattr_virt, size, 0);
382         mutex_unlock(&lower_inode->i_mutex);
383         if (rc)
384                 printk(KERN_ERR "Error whilst attempting to write inode size "
385                        "to lower file xattr; rc = [%d]\n", rc);
386         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
387 out:
388         return rc;
389 }
390
391 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
392 {
393         struct ecryptfs_crypt_stat *crypt_stat;
394
395         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
396         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
397                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
398         else
399                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
400 }
401
402 /**
403  * ecryptfs_commit_write
404  * @file: The eCryptfs file object
405  * @page: The eCryptfs page
406  * @from: Ignored (we rotate the page IV on each write)
407  * @to: Ignored
408  *
409  * This is where we encrypt the data and pass the encrypted data to
410  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
411  * entire underlying packets.
412  */
413 static int ecryptfs_commit_write(struct file *file, struct page *page,
414                                  unsigned from, unsigned to)
415 {
416         loff_t pos;
417         struct inode *ecryptfs_inode = page->mapping->host;
418         struct ecryptfs_crypt_stat *crypt_stat =
419                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
420         int rc;
421
422         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
423                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
424                         "crypt_stat at memory location [%p]\n", crypt_stat);
425                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
426         } else
427                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
428         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
429                         "(page w/ index = [0x%.16x], to = [%d])\n", page->index,
430                         to);
431         /* Fills in zeros if 'to' goes beyond inode size */
432         rc = fill_zeros_to_end_of_page(page, to);
433         if (rc) {
434                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
435                                 "zeros in page with index = [0x%.16x]\n",
436                                 page->index);
437                 goto out;
438         }
439         rc = ecryptfs_encrypt_page(page);
440         if (rc) {
441                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
442                                 "index [0x%.16x])\n", page->index);
443                 goto out;
444         }
445         pos = (((loff_t)page->index) << PAGE_CACHE_SHIFT) + to;
446         if (pos > i_size_read(ecryptfs_inode)) {
447                 i_size_write(ecryptfs_inode, pos);
448                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
449                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
450         }
451         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
452         if (rc)
453                 printk(KERN_ERR "Error writing inode size to metadata; "
454                        "rc = [%d]\n", rc);
455 out:
456         return rc;
457 }
458
459 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
460 {
461         int rc = 0;
462         struct inode *inode;
463         struct inode *lower_inode;
464
465         inode = (struct inode *)mapping->host;
466         lower_inode = ecryptfs_inode_to_lower(inode);
467         if (lower_inode->i_mapping->a_ops->bmap)
468                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
469                                                          block);
470         return rc;
471 }
472
473 struct address_space_operations ecryptfs_aops = {
474         .writepage = ecryptfs_writepage,
475         .readpage = ecryptfs_readpage,
476         .prepare_write = ecryptfs_prepare_write,
477         .commit_write = ecryptfs_commit_write,
478         .bmap = ecryptfs_bmap,
479 };