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TOMOYO Linux Cross Reference
Linux/fs/ecryptfs/mmap.c

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  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/scatterlist.h>
 34 #include <linux/slab.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 inode *inode, loff_t index)
 47 {
 48         struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
 49         if (!IS_ERR(page))
 50                 lock_page(page);
 51         return page;
 52 }
 53 
 54 /**
 55  * ecryptfs_writepage
 56  * @page: Page that is locked before this call is made
 57  *
 58  * Returns zero on success; non-zero otherwise
 59  *
 60  * This is where we encrypt the data and pass the encrypted data to
 61  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 62  * entire underlying packets.
 63  */
 64 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
 65 {
 66         int rc;
 67 
 68         rc = ecryptfs_encrypt_page(page);
 69         if (rc) {
 70                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
 71                                 "page (upper index [0x%.16lx])\n", page->index);
 72                 ClearPageUptodate(page);
 73                 goto out;
 74         }
 75         SetPageUptodate(page);
 76 out:
 77         unlock_page(page);
 78         return rc;
 79 }
 80 
 81 static void strip_xattr_flag(char *page_virt,
 82                              struct ecryptfs_crypt_stat *crypt_stat)
 83 {
 84         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 85                 size_t written;
 86 
 87                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
 88                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
 89                                                 &written);
 90                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
 91         }
 92 }
 93 
 94 /**
 95  *   Header Extent:
 96  *     Octets 0-7:        Unencrypted file size (big-endian)
 97  *     Octets 8-15:       eCryptfs special marker
 98  *     Octets 16-19:      Flags
 99  *      Octet 16:         File format version number (between 0 and 255)
100  *      Octets 17-18:     Reserved
101  *      Octet 19:         Bit 1 (lsb): Reserved
102  *                        Bit 2: Encrypted?
103  *                        Bits 3-8: Reserved
104  *     Octets 20-23:      Header extent size (big-endian)
105  *     Octets 24-25:      Number of header extents at front of file
106  *                        (big-endian)
107  *     Octet  26:         Begin RFC 2440 authentication token packet set
108  */
109 
110 /**
111  * ecryptfs_copy_up_encrypted_with_header
112  * @page: Sort of a ``virtual'' representation of the encrypted lower
113  *        file. The actual lower file does not have the metadata in
114  *        the header. This is locked.
115  * @crypt_stat: The eCryptfs inode's cryptographic context
116  *
117  * The ``view'' is the version of the file that userspace winds up
118  * seeing, with the header information inserted.
119  */
120 static int
121 ecryptfs_copy_up_encrypted_with_header(struct page *page,
122                                        struct ecryptfs_crypt_stat *crypt_stat)
123 {
124         loff_t extent_num_in_page = 0;
125         loff_t num_extents_per_page = (PAGE_SIZE
126                                        / crypt_stat->extent_size);
127         int rc = 0;
128 
129         while (extent_num_in_page < num_extents_per_page) {
130                 loff_t view_extent_num = ((((loff_t)page->index)
131                                            * num_extents_per_page)
132                                           + extent_num_in_page);
133                 size_t num_header_extents_at_front =
134                         (crypt_stat->metadata_size / crypt_stat->extent_size);
135 
136                 if (view_extent_num < num_header_extents_at_front) {
137                         /* This is a header extent */
138                         char *page_virt;
139 
140                         page_virt = kmap_atomic(page);
141                         memset(page_virt, 0, PAGE_SIZE);
142                         /* TODO: Support more than one header extent */
143                         if (view_extent_num == 0) {
144                                 size_t written;
145 
146                                 rc = ecryptfs_read_xattr_region(
147                                         page_virt, page->mapping->host);
148                                 strip_xattr_flag(page_virt + 16, crypt_stat);
149                                 ecryptfs_write_header_metadata(page_virt + 20,
150                                                                crypt_stat,
151                                                                &written);
152                         }
153                         kunmap_atomic(page_virt);
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->metadata_size);
165 
166                         rc = ecryptfs_read_lower_page_segment(
167                                 page, (lower_offset >> PAGE_SHIFT),
168                                 (lower_offset & ~PAGE_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(page->mapping->host)->crypt_stat;
197         int rc = 0;
198 
199         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
200                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
201                                                       PAGE_SIZE,
202                                                       page->mapping->host);
203         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
204                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
205                         rc = ecryptfs_copy_up_encrypted_with_header(page,
206                                                                     crypt_stat);
207                         if (rc) {
208                                 printk(KERN_ERR "%s: Error attempting to copy "
209                                        "the encrypted content from the lower "
210                                        "file whilst inserting the metadata "
211                                        "from the xattr into the header; rc = "
212                                        "[%d]\n", __func__, rc);
213                                 goto out;
214                         }
215 
216                 } else {
217                         rc = ecryptfs_read_lower_page_segment(
218                                 page, page->index, 0, PAGE_SIZE,
219                                 page->mapping->host);
220                         if (rc) {
221                                 printk(KERN_ERR "Error reading page; rc = "
222                                        "[%d]\n", rc);
223                                 goto out;
224                         }
225                 }
226         } else {
227                 rc = ecryptfs_decrypt_page(page);
228                 if (rc) {
229                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
230                                         "rc = [%d]\n", rc);
231                         goto out;
232                 }
233         }
234 out:
235         if (rc)
236                 ClearPageUptodate(page);
237         else
238                 SetPageUptodate(page);
239         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
240                         page->index);
241         unlock_page(page);
242         return rc;
243 }
244 
245 /**
246  * Called with lower inode mutex held.
247  */
248 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
249 {
250         struct inode *inode = page->mapping->host;
251         int end_byte_in_page;
252 
253         if ((i_size_read(inode) / PAGE_SIZE) != page->index)
254                 goto out;
255         end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
256         if (to > end_byte_in_page)
257                 end_byte_in_page = to;
258         zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
259 out:
260         return 0;
261 }
262 
263 /**
264  * ecryptfs_write_begin
265  * @file: The eCryptfs file
266  * @mapping: The eCryptfs object
267  * @pos: The file offset at which to start writing
268  * @len: Length of the write
269  * @flags: Various flags
270  * @pagep: Pointer to return the page
271  * @fsdata: Pointer to return fs data (unused)
272  *
273  * This function must zero any hole we create
274  *
275  * Returns zero on success; non-zero otherwise
276  */
277 static int ecryptfs_write_begin(struct file *file,
278                         struct address_space *mapping,
279                         loff_t pos, unsigned len, unsigned flags,
280                         struct page **pagep, void **fsdata)
281 {
282         pgoff_t index = pos >> PAGE_SHIFT;
283         struct page *page;
284         loff_t prev_page_end_size;
285         int rc = 0;
286 
287         page = grab_cache_page_write_begin(mapping, index, flags);
288         if (!page)
289                 return -ENOMEM;
290         *pagep = page;
291 
292         prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
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                         rc = ecryptfs_read_lower_page_segment(
299                                 page, index, 0, PAGE_SIZE, mapping->host);
300                         if (rc) {
301                                 printk(KERN_ERR "%s: Error attempting to read "
302                                        "lower page segment; rc = [%d]\n",
303                                        __func__, rc);
304                                 ClearPageUptodate(page);
305                                 goto out;
306                         } else
307                                 SetPageUptodate(page);
308                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
309                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
310                                 rc = ecryptfs_copy_up_encrypted_with_header(
311                                         page, crypt_stat);
312                                 if (rc) {
313                                         printk(KERN_ERR "%s: Error attempting "
314                                                "to copy the encrypted content "
315                                                "from the lower file whilst "
316                                                "inserting the metadata from "
317                                                "the xattr into the header; rc "
318                                                "= [%d]\n", __func__, rc);
319                                         ClearPageUptodate(page);
320                                         goto out;
321                                 }
322                                 SetPageUptodate(page);
323                         } else {
324                                 rc = ecryptfs_read_lower_page_segment(
325                                         page, index, 0, PAGE_SIZE,
326                                         mapping->host);
327                                 if (rc) {
328                                         printk(KERN_ERR "%s: Error reading "
329                                                "page; rc = [%d]\n",
330                                                __func__, rc);
331                                         ClearPageUptodate(page);
332                                         goto out;
333                                 }
334                                 SetPageUptodate(page);
335                         }
336                 } else {
337                         if (prev_page_end_size
338                             >= i_size_read(page->mapping->host)) {
339                                 zero_user(page, 0, PAGE_SIZE);
340                                 SetPageUptodate(page);
341                         } else if (len < PAGE_SIZE) {
342                                 rc = ecryptfs_decrypt_page(page);
343                                 if (rc) {
344                                         printk(KERN_ERR "%s: Error decrypting "
345                                                "page at index [%ld]; "
346                                                "rc = [%d]\n",
347                                                __func__, page->index, rc);
348                                         ClearPageUptodate(page);
349                                         goto out;
350                                 }
351                                 SetPageUptodate(page);
352                         }
353                 }
354         }
355         /* If creating a page or more of holes, zero them out via truncate.
356          * Note, this will increase i_size. */
357         if (index != 0) {
358                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
359                         rc = ecryptfs_truncate(file->f_path.dentry,
360                                                prev_page_end_size);
361                         if (rc) {
362                                 printk(KERN_ERR "%s: Error on attempt to "
363                                        "truncate to (higher) offset [%lld];"
364                                        " rc = [%d]\n", __func__,
365                                        prev_page_end_size, rc);
366                                 goto out;
367                         }
368                 }
369         }
370         /* Writing to a new page, and creating a small hole from start
371          * of page?  Zero it out. */
372         if ((i_size_read(mapping->host) == prev_page_end_size)
373             && (pos != 0))
374                 zero_user(page, 0, PAGE_SIZE);
375 out:
376         if (unlikely(rc)) {
377                 unlock_page(page);
378                 put_page(page);
379                 *pagep = NULL;
380         }
381         return rc;
382 }
383 
384 /**
385  * ecryptfs_write_inode_size_to_header
386  *
387  * Writes the lower file size to the first 8 bytes of the header.
388  *
389  * Returns zero on success; non-zero on error.
390  */
391 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
392 {
393         char *file_size_virt;
394         int rc;
395 
396         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
397         if (!file_size_virt) {
398                 rc = -ENOMEM;
399                 goto out;
400         }
401         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
402         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
403                                   sizeof(u64));
404         kfree(file_size_virt);
405         if (rc < 0)
406                 printk(KERN_ERR "%s: Error writing file size to header; "
407                        "rc = [%d]\n", __func__, rc);
408         else
409                 rc = 0;
410 out:
411         return rc;
412 }
413 
414 struct kmem_cache *ecryptfs_xattr_cache;
415 
416 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
417 {
418         ssize_t size;
419         void *xattr_virt;
420         struct dentry *lower_dentry =
421                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
422         struct inode *lower_inode = d_inode(lower_dentry);
423         int rc;
424 
425         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
426                 printk(KERN_WARNING
427                        "No support for setting xattr in lower filesystem\n");
428                 rc = -ENOSYS;
429                 goto out;
430         }
431         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
432         if (!xattr_virt) {
433                 printk(KERN_ERR "Out of memory whilst attempting to write "
434                        "inode size to xattr\n");
435                 rc = -ENOMEM;
436                 goto out;
437         }
438         inode_lock(lower_inode);
439         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
440                                            xattr_virt, PAGE_SIZE);
441         if (size < 0)
442                 size = 8;
443         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
444         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
445                                          xattr_virt, size, 0);
446         inode_unlock(lower_inode);
447         if (rc)
448                 printk(KERN_ERR "Error whilst attempting to write inode size "
449                        "to lower file xattr; rc = [%d]\n", rc);
450         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
451 out:
452         return rc;
453 }
454 
455 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
456 {
457         struct ecryptfs_crypt_stat *crypt_stat;
458 
459         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
460         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
461         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
462                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
463         else
464                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
465 }
466 
467 /**
468  * ecryptfs_write_end
469  * @file: The eCryptfs file object
470  * @mapping: The eCryptfs object
471  * @pos: The file position
472  * @len: The length of the data (unused)
473  * @copied: The amount of data copied
474  * @page: The eCryptfs page
475  * @fsdata: The fsdata (unused)
476  */
477 static int ecryptfs_write_end(struct file *file,
478                         struct address_space *mapping,
479                         loff_t pos, unsigned len, unsigned copied,
480                         struct page *page, void *fsdata)
481 {
482         pgoff_t index = pos >> PAGE_SHIFT;
483         unsigned from = pos & (PAGE_SIZE - 1);
484         unsigned to = from + copied;
485         struct inode *ecryptfs_inode = mapping->host;
486         struct ecryptfs_crypt_stat *crypt_stat =
487                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
488         int rc;
489 
490         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
491                         "(page w/ index = [0x%.16lx], 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         if (!PageUptodate(page)) {
503                 if (copied < PAGE_SIZE) {
504                         rc = 0;
505                         goto out;
506                 }
507                 SetPageUptodate(page);
508         }
509         /* Fills in zeros if 'to' goes beyond inode size */
510         rc = fill_zeros_to_end_of_page(page, to);
511         if (rc) {
512                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
513                         "zeros in page with index = [0x%.16lx]\n", index);
514                 goto out;
515         }
516         rc = ecryptfs_encrypt_page(page);
517         if (rc) {
518                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
519                                 "index [0x%.16lx])\n", index);
520                 goto out;
521         }
522         if (pos + copied > i_size_read(ecryptfs_inode)) {
523                 i_size_write(ecryptfs_inode, pos + copied);
524                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
525                         "[0x%.16llx]\n",
526                         (unsigned long long)i_size_read(ecryptfs_inode));
527         }
528         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
529         if (rc)
530                 printk(KERN_ERR "Error writing inode size to metadata; "
531                        "rc = [%d]\n", rc);
532         else
533                 rc = copied;
534 out:
535         unlock_page(page);
536         put_page(page);
537         return rc;
538 }
539 
540 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
541 {
542         int rc = 0;
543         struct inode *inode;
544         struct inode *lower_inode;
545 
546         inode = (struct inode *)mapping->host;
547         lower_inode = ecryptfs_inode_to_lower(inode);
548         if (lower_inode->i_mapping->a_ops->bmap)
549                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
550                                                          block);
551         return rc;
552 }
553 
554 const struct address_space_operations ecryptfs_aops = {
555         .writepage = ecryptfs_writepage,
556         .readpage = ecryptfs_readpage,
557         .write_begin = ecryptfs_write_begin,
558         .write_end = ecryptfs_write_end,
559         .bmap = ecryptfs_bmap,
560 };
561 

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