vmscan: fix shrinker callback bug in fs/super.c
[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         /*
66          * Refuse to write the page out if we are called from reclaim context
67          * since our writepage() path may potentially allocate memory when
68          * calling into the lower fs vfs_write() which may in turn invoke
69          * us again.
70          */
71         if (current->flags & PF_MEMALLOC) {
72                 redirty_page_for_writepage(wbc, page);
73                 rc = 0;
74                 goto out;
75         }
76
77         rc = ecryptfs_encrypt_page(page);
78         if (rc) {
79                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
80                                 "page (upper index [0x%.16lx])\n", page->index);
81                 ClearPageUptodate(page);
82                 goto out;
83         }
84         SetPageUptodate(page);
85 out:
86         unlock_page(page);
87         return rc;
88 }
89
90 static void strip_xattr_flag(char *page_virt,
91                              struct ecryptfs_crypt_stat *crypt_stat)
92 {
93         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
94                 size_t written;
95
96                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
97                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
98                                                 &written);
99                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
100         }
101 }
102
103 /**
104  *   Header Extent:
105  *     Octets 0-7:        Unencrypted file size (big-endian)
106  *     Octets 8-15:       eCryptfs special marker
107  *     Octets 16-19:      Flags
108  *      Octet 16:         File format version number (between 0 and 255)
109  *      Octets 17-18:     Reserved
110  *      Octet 19:         Bit 1 (lsb): Reserved
111  *                        Bit 2: Encrypted?
112  *                        Bits 3-8: Reserved
113  *     Octets 20-23:      Header extent size (big-endian)
114  *     Octets 24-25:      Number of header extents at front of file
115  *                        (big-endian)
116  *     Octet  26:         Begin RFC 2440 authentication token packet set
117  */
118
119 /**
120  * ecryptfs_copy_up_encrypted_with_header
121  * @page: Sort of a ``virtual'' representation of the encrypted lower
122  *        file. The actual lower file does not have the metadata in
123  *        the header. This is locked.
124  * @crypt_stat: The eCryptfs inode's cryptographic context
125  *
126  * The ``view'' is the version of the file that userspace winds up
127  * seeing, with the header information inserted.
128  */
129 static int
130 ecryptfs_copy_up_encrypted_with_header(struct page *page,
131                                        struct ecryptfs_crypt_stat *crypt_stat)
132 {
133         loff_t extent_num_in_page = 0;
134         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
135                                        / crypt_stat->extent_size);
136         int rc = 0;
137
138         while (extent_num_in_page < num_extents_per_page) {
139                 loff_t view_extent_num = ((((loff_t)page->index)
140                                            * num_extents_per_page)
141                                           + extent_num_in_page);
142                 size_t num_header_extents_at_front =
143                         (crypt_stat->metadata_size / crypt_stat->extent_size);
144
145                 if (view_extent_num < num_header_extents_at_front) {
146                         /* This is a header extent */
147                         char *page_virt;
148
149                         page_virt = kmap_atomic(page, KM_USER0);
150                         memset(page_virt, 0, PAGE_CACHE_SIZE);
151                         /* TODO: Support more than one header extent */
152                         if (view_extent_num == 0) {
153                                 size_t written;
154
155                                 rc = ecryptfs_read_xattr_region(
156                                         page_virt, page->mapping->host);
157                                 strip_xattr_flag(page_virt + 16, crypt_stat);
158                                 ecryptfs_write_header_metadata(page_virt + 20,
159                                                                crypt_stat,
160                                                                &written);
161                         }
162                         kunmap_atomic(page_virt, KM_USER0);
163                         flush_dcache_page(page);
164                         if (rc) {
165                                 printk(KERN_ERR "%s: Error reading xattr "
166                                        "region; rc = [%d]\n", __func__, rc);
167                                 goto out;
168                         }
169                 } else {
170                         /* This is an encrypted data extent */
171                         loff_t lower_offset =
172                                 ((view_extent_num * crypt_stat->extent_size)
173                                  - crypt_stat->metadata_size);
174
175                         rc = ecryptfs_read_lower_page_segment(
176                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
177                                 (lower_offset & ~PAGE_CACHE_MASK),
178                                 crypt_stat->extent_size, page->mapping->host);
179                         if (rc) {
180                                 printk(KERN_ERR "%s: Error attempting to read "
181                                        "extent at offset [%lld] in the lower "
182                                        "file; rc = [%d]\n", __func__,
183                                        lower_offset, rc);
184                                 goto out;
185                         }
186                 }
187                 extent_num_in_page++;
188         }
189 out:
190         return rc;
191 }
192
193 /**
194  * ecryptfs_readpage
195  * @file: An eCryptfs file
196  * @page: Page from eCryptfs inode mapping into which to stick the read data
197  *
198  * Read in a page, decrypting if necessary.
199  *
200  * Returns zero on success; non-zero on error.
201  */
202 static int ecryptfs_readpage(struct file *file, struct page *page)
203 {
204         struct ecryptfs_crypt_stat *crypt_stat =
205                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
206         int rc = 0;
207
208         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
209                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
210                                                       PAGE_CACHE_SIZE,
211                                                       page->mapping->host);
212         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
213                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
214                         rc = ecryptfs_copy_up_encrypted_with_header(page,
215                                                                     crypt_stat);
216                         if (rc) {
217                                 printk(KERN_ERR "%s: Error attempting to copy "
218                                        "the encrypted content from the lower "
219                                        "file whilst inserting the metadata "
220                                        "from the xattr into the header; rc = "
221                                        "[%d]\n", __func__, rc);
222                                 goto out;
223                         }
224
225                 } else {
226                         rc = ecryptfs_read_lower_page_segment(
227                                 page, page->index, 0, PAGE_CACHE_SIZE,
228                                 page->mapping->host);
229                         if (rc) {
230                                 printk(KERN_ERR "Error reading page; rc = "
231                                        "[%d]\n", rc);
232                                 goto out;
233                         }
234                 }
235         } else {
236                 rc = ecryptfs_decrypt_page(page);
237                 if (rc) {
238                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
239                                         "rc = [%d]\n", rc);
240                         goto out;
241                 }
242         }
243 out:
244         if (rc)
245                 ClearPageUptodate(page);
246         else
247                 SetPageUptodate(page);
248         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
249                         page->index);
250         unlock_page(page);
251         return rc;
252 }
253
254 /**
255  * Called with lower inode mutex held.
256  */
257 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
258 {
259         struct inode *inode = page->mapping->host;
260         int end_byte_in_page;
261
262         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
263                 goto out;
264         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
265         if (to > end_byte_in_page)
266                 end_byte_in_page = to;
267         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
268 out:
269         return 0;
270 }
271
272 /**
273  * ecryptfs_write_begin
274  * @file: The eCryptfs file
275  * @mapping: The eCryptfs object
276  * @pos: The file offset at which to start writing
277  * @len: Length of the write
278  * @flags: Various flags
279  * @pagep: Pointer to return the page
280  * @fsdata: Pointer to return fs data (unused)
281  *
282  * This function must zero any hole we create
283  *
284  * Returns zero on success; non-zero otherwise
285  */
286 static int ecryptfs_write_begin(struct file *file,
287                         struct address_space *mapping,
288                         loff_t pos, unsigned len, unsigned flags,
289                         struct page **pagep, void **fsdata)
290 {
291         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
292         struct page *page;
293         loff_t prev_page_end_size;
294         int rc = 0;
295
296         page = grab_cache_page_write_begin(mapping, index, flags);
297         if (!page)
298                 return -ENOMEM;
299         *pagep = page;
300
301         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
302         if (!PageUptodate(page)) {
303                 struct ecryptfs_crypt_stat *crypt_stat =
304                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
305
306                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
307                         rc = ecryptfs_read_lower_page_segment(
308                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
309                         if (rc) {
310                                 printk(KERN_ERR "%s: Error attemping to read "
311                                        "lower page segment; rc = [%d]\n",
312                                        __func__, rc);
313                                 ClearPageUptodate(page);
314                                 goto out;
315                         } else
316                                 SetPageUptodate(page);
317                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
318                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
319                                 rc = ecryptfs_copy_up_encrypted_with_header(
320                                         page, crypt_stat);
321                                 if (rc) {
322                                         printk(KERN_ERR "%s: Error attempting "
323                                                "to copy the encrypted content "
324                                                "from the lower file whilst "
325                                                "inserting the metadata from "
326                                                "the xattr into the header; rc "
327                                                "= [%d]\n", __func__, rc);
328                                         ClearPageUptodate(page);
329                                         goto out;
330                                 }
331                                 SetPageUptodate(page);
332                         } else {
333                                 rc = ecryptfs_read_lower_page_segment(
334                                         page, index, 0, PAGE_CACHE_SIZE,
335                                         mapping->host);
336                                 if (rc) {
337                                         printk(KERN_ERR "%s: Error reading "
338                                                "page; rc = [%d]\n",
339                                                __func__, rc);
340                                         ClearPageUptodate(page);
341                                         goto out;
342                                 }
343                                 SetPageUptodate(page);
344                         }
345                 } else {
346                         if (prev_page_end_size
347                             >= i_size_read(page->mapping->host)) {
348                                 zero_user(page, 0, PAGE_CACHE_SIZE);
349                         } else {
350                                 rc = ecryptfs_decrypt_page(page);
351                                 if (rc) {
352                                         printk(KERN_ERR "%s: Error decrypting "
353                                                "page at index [%ld]; "
354                                                "rc = [%d]\n",
355                                                __func__, page->index, rc);
356                                         ClearPageUptodate(page);
357                                         goto out;
358                                 }
359                         }
360                         SetPageUptodate(page);
361                 }
362         }
363         /* If creating a page or more of holes, zero them out via truncate.
364          * Note, this will increase i_size. */
365         if (index != 0) {
366                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
367                         rc = ecryptfs_truncate(file->f_path.dentry,
368                                                prev_page_end_size);
369                         if (rc) {
370                                 printk(KERN_ERR "%s: Error on attempt to "
371                                        "truncate to (higher) offset [%lld];"
372                                        " rc = [%d]\n", __func__,
373                                        prev_page_end_size, rc);
374                                 goto out;
375                         }
376                 }
377         }
378         /* Writing to a new page, and creating a small hole from start
379          * of page?  Zero it out. */
380         if ((i_size_read(mapping->host) == prev_page_end_size)
381             && (pos != 0))
382                 zero_user(page, 0, PAGE_CACHE_SIZE);
383 out:
384         if (unlikely(rc)) {
385                 unlock_page(page);
386                 page_cache_release(page);
387                 *pagep = NULL;
388         }
389         return rc;
390 }
391
392 /**
393  * ecryptfs_write_inode_size_to_header
394  *
395  * Writes the lower file size to the first 8 bytes of the header.
396  *
397  * Returns zero on success; non-zero on error.
398  */
399 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
400 {
401         char *file_size_virt;
402         int rc;
403
404         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
405         if (!file_size_virt) {
406                 rc = -ENOMEM;
407                 goto out;
408         }
409         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
410         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
411                                   sizeof(u64));
412         kfree(file_size_virt);
413         if (rc < 0)
414                 printk(KERN_ERR "%s: Error writing file size to header; "
415                        "rc = [%d]\n", __func__, rc);
416         else
417                 rc = 0;
418 out:
419         return rc;
420 }
421
422 struct kmem_cache *ecryptfs_xattr_cache;
423
424 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
425 {
426         ssize_t size;
427         void *xattr_virt;
428         struct dentry *lower_dentry =
429                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
430         struct inode *lower_inode = lower_dentry->d_inode;
431         int rc;
432
433         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
434                 printk(KERN_WARNING
435                        "No support for setting xattr in lower filesystem\n");
436                 rc = -ENOSYS;
437                 goto out;
438         }
439         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
440         if (!xattr_virt) {
441                 printk(KERN_ERR "Out of memory whilst attempting to write "
442                        "inode size to xattr\n");
443                 rc = -ENOMEM;
444                 goto out;
445         }
446         mutex_lock(&lower_inode->i_mutex);
447         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
448                                            xattr_virt, PAGE_CACHE_SIZE);
449         if (size < 0)
450                 size = 8;
451         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
452         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
453                                          xattr_virt, size, 0);
454         mutex_unlock(&lower_inode->i_mutex);
455         if (rc)
456                 printk(KERN_ERR "Error whilst attempting to write inode size "
457                        "to lower file xattr; rc = [%d]\n", rc);
458         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
459 out:
460         return rc;
461 }
462
463 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
464 {
465         struct ecryptfs_crypt_stat *crypt_stat;
466
467         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
468         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
469         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
470                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
471         else
472                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
473 }
474
475 /**
476  * ecryptfs_write_end
477  * @file: The eCryptfs file object
478  * @mapping: The eCryptfs object
479  * @pos: The file position
480  * @len: The length of the data (unused)
481  * @copied: The amount of data copied
482  * @page: The eCryptfs page
483  * @fsdata: The fsdata (unused)
484  *
485  * This is where we encrypt the data and pass the encrypted data to
486  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
487  * entire underlying packets.
488  */
489 static int ecryptfs_write_end(struct file *file,
490                         struct address_space *mapping,
491                         loff_t pos, unsigned len, unsigned copied,
492                         struct page *page, void *fsdata)
493 {
494         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
495         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
496         unsigned to = from + copied;
497         struct inode *ecryptfs_inode = mapping->host;
498         struct ecryptfs_crypt_stat *crypt_stat =
499                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
500         int rc;
501         int need_unlock_page = 1;
502
503         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
504                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
505         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
506                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
507                                                        to);
508                 if (!rc) {
509                         rc = copied;
510                         fsstack_copy_inode_size(ecryptfs_inode,
511                                 ecryptfs_inode_to_lower(ecryptfs_inode));
512                 }
513                 goto out;
514         }
515         /* Fills in zeros if 'to' goes beyond inode size */
516         rc = fill_zeros_to_end_of_page(page, to);
517         if (rc) {
518                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
519                         "zeros in page with index = [0x%.16lx]\n", index);
520                 goto out;
521         }
522         set_page_dirty(page);
523         unlock_page(page);
524         need_unlock_page = 0;
525         if (pos + copied > i_size_read(ecryptfs_inode)) {
526                 i_size_write(ecryptfs_inode, pos + copied);
527                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
528                         "[0x%.16llx]\n",
529                         (unsigned long long)i_size_read(ecryptfs_inode));
530                 balance_dirty_pages_ratelimited(mapping);
531                 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
532                 if (rc) {
533                         printk(KERN_ERR "Error writing inode size to metadata; "
534                                "rc = [%d]\n", rc);
535                         goto out;
536                 }
537         }
538         rc = copied;
539 out:
540         if (need_unlock_page)
541                 unlock_page(page);
542         page_cache_release(page);
543         return rc;
544 }
545
546 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
547 {
548         int rc = 0;
549         struct inode *inode;
550         struct inode *lower_inode;
551
552         inode = (struct inode *)mapping->host;
553         lower_inode = ecryptfs_inode_to_lower(inode);
554         if (lower_inode->i_mapping->a_ops->bmap)
555                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
556                                                          block);
557         return rc;
558 }
559
560 const struct address_space_operations ecryptfs_aops = {
561         .writepage = ecryptfs_writepage,
562         .readpage = ecryptfs_readpage,
563         .write_begin = ecryptfs_write_begin,
564         .write_end = ecryptfs_write_end,
565         .bmap = ecryptfs_bmap,
566 };