2 * eCryptfs: Linux filesystem encryption layer
4 * Copyright (C) 2007 International Business Machines Corp.
5 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License as
9 * published by the Free Software Foundation; either version 2 of the
10 * License, or (at your option) any later version.
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
24 #include <linux/pagemap.h>
25 #include "ecryptfs_kernel.h"
28 * ecryptfs_write_lower
29 * @ecryptfs_inode: The eCryptfs inode
30 * @data: Data to write
31 * @offset: Byte offset in the lower file to which to write the data
32 * @size: Number of bytes from @data to write at @offset in the lower
35 * Write data to the lower file.
37 * Returns bytes written on success; less than zero on error
39 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
40 loff_t offset, size_t size)
42 struct ecryptfs_inode_info *inode_info;
46 inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
47 BUG_ON(!inode_info->lower_file);
50 rc = vfs_write(inode_info->lower_file, data, size, &offset);
52 mark_inode_dirty_sync(ecryptfs_inode);
57 * ecryptfs_write_lower_page_segment
58 * @ecryptfs_inode: The eCryptfs inode
59 * @page_for_lower: The page containing the data to be written to the
61 * @offset_in_page: The offset in the @page_for_lower from which to
62 * start writing the data
63 * @size: The amount of data from @page_for_lower to write to the
66 * Determines the byte offset in the file for the given page and
67 * offset within the page, maps the page, and makes the call to write
68 * the contents of @page_for_lower to the lower inode.
70 * Returns zero on success; non-zero otherwise
72 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
73 struct page *page_for_lower,
74 size_t offset_in_page, size_t size)
80 offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
82 virt = kmap(page_for_lower);
83 rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
86 kunmap(page_for_lower);
92 * @ecryptfs_inode: The eCryptfs file into which to write
93 * @data: Virtual address where data to write is located
94 * @offset: Offset in the eCryptfs file at which to begin writing the
96 * @size: The number of bytes to write from @data
98 * Write an arbitrary amount of data to an arbitrary location in the
99 * eCryptfs inode page cache. This is done on a page-by-page, and then
100 * by an extent-by-extent, basis; individual extents are encrypted and
101 * written to the lower page cache (via VFS writes). This function
102 * takes care of all the address translation to locations in the lower
103 * filesystem; it also handles truncate events, writing out zeros
106 * Returns zero on success; non-zero otherwise
108 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
111 struct page *ecryptfs_page;
112 struct ecryptfs_crypt_stat *crypt_stat;
113 char *ecryptfs_page_virt;
114 loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
115 loff_t data_offset = 0;
119 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
121 * if we are writing beyond current size, then start pos
122 * at the current size - we'll fill in zeros from there.
124 if (offset > ecryptfs_file_size)
125 pos = ecryptfs_file_size;
128 while (pos < (offset + size)) {
129 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
130 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
131 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
132 size_t total_remaining_bytes = ((offset + size) - pos);
134 if (num_bytes > total_remaining_bytes)
135 num_bytes = total_remaining_bytes;
137 /* remaining zeros to write, up to destination offset */
138 size_t total_remaining_zeros = (offset - pos);
140 if (num_bytes > total_remaining_zeros)
141 num_bytes = total_remaining_zeros;
143 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
145 if (IS_ERR(ecryptfs_page)) {
146 rc = PTR_ERR(ecryptfs_page);
147 printk(KERN_ERR "%s: Error getting page at "
148 "index [%ld] from eCryptfs inode "
149 "mapping; rc = [%d]\n", __func__,
150 ecryptfs_page_idx, rc);
153 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
156 * pos: where we're now writing, offset: where the request was
157 * If current pos is before request, we are filling zeros
158 * If we are at or beyond request, we are writing the *data*
159 * If we're in a fresh page beyond eof, zero it in either case
161 if (pos < offset || !start_offset_in_page) {
162 /* We are extending past the previous end of the file.
163 * Fill in zero values to the end of the page */
164 memset(((char *)ecryptfs_page_virt
165 + start_offset_in_page), 0,
166 PAGE_CACHE_SIZE - start_offset_in_page);
169 /* pos >= offset, we are now writing the data request */
171 memcpy(((char *)ecryptfs_page_virt
172 + start_offset_in_page),
173 (data + data_offset), num_bytes);
174 data_offset += num_bytes;
176 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
177 flush_dcache_page(ecryptfs_page);
178 SetPageUptodate(ecryptfs_page);
179 unlock_page(ecryptfs_page);
180 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
181 rc = ecryptfs_encrypt_page(ecryptfs_page);
183 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
185 start_offset_in_page,
187 page_cache_release(ecryptfs_page);
189 printk(KERN_ERR "%s: Error encrypting "
190 "page; rc = [%d]\n", __func__, rc);
195 if ((offset + size) > ecryptfs_file_size) {
196 i_size_write(ecryptfs_inode, (offset + size));
197 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
198 rc = ecryptfs_write_inode_size_to_metadata(
201 printk(KERN_ERR "Problem with "
202 "ecryptfs_write_inode_size_to_metadata; "
213 * ecryptfs_read_lower
214 * @data: The read data is stored here by this function
215 * @offset: Byte offset in the lower file from which to read the data
216 * @size: Number of bytes to read from @offset of the lower file and
218 * @ecryptfs_inode: The eCryptfs inode
220 * Read @size bytes of data at byte offset @offset from the lower
221 * inode into memory location @data.
223 * Returns bytes read on success; 0 on EOF; less than zero on error
225 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
226 struct inode *ecryptfs_inode)
228 struct ecryptfs_inode_info *inode_info =
229 ecryptfs_inode_to_private(ecryptfs_inode);
230 mm_segment_t fs_save;
233 BUG_ON(!inode_info->lower_file);
236 rc = vfs_read(inode_info->lower_file, data, size, &offset);
242 * ecryptfs_read_lower_page_segment
243 * @page_for_ecryptfs: The page into which data for eCryptfs will be
245 * @offset_in_page: Offset in @page_for_ecryptfs from which to start
247 * @size: The number of bytes to write into @page_for_ecryptfs
248 * @ecryptfs_inode: The eCryptfs inode
250 * Determines the byte offset in the file for the given page and
251 * offset within the page, maps the page, and makes the call to read
252 * the contents of @page_for_ecryptfs from the lower inode.
254 * Returns zero on success; non-zero otherwise
256 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
258 size_t offset_in_page, size_t size,
259 struct inode *ecryptfs_inode)
265 offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
266 virt = kmap(page_for_ecryptfs);
267 rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
270 kunmap(page_for_ecryptfs);
271 flush_dcache_page(page_for_ecryptfs);
278 * @data: The virtual address into which to write the data read (and
279 * possibly decrypted) from the lower file
280 * @offset: The offset in the decrypted view of the file from which to
282 * @size: The number of bytes to read into @data
283 * @ecryptfs_file: The eCryptfs file from which to read
285 * Read an arbitrary amount of data from an arbitrary location in the
286 * eCryptfs page cache. This is done on an extent-by-extent basis;
287 * individual extents are decrypted and read from the lower page
288 * cache (via VFS reads). This function takes care of all the
289 * address translation to locations in the lower filesystem.
291 * Returns zero on success; non-zero otherwise
293 int ecryptfs_read(char *data, loff_t offset, size_t size,
294 struct file *ecryptfs_file)
296 struct inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode;
297 struct page *ecryptfs_page;
298 char *ecryptfs_page_virt;
299 loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
300 loff_t data_offset = 0;
304 if ((offset + size) > ecryptfs_file_size) {
306 printk(KERN_ERR "%s: Attempt to read data past the end of the "
307 "file; offset = [%lld]; size = [%td]; "
308 "ecryptfs_file_size = [%lld]\n",
309 __func__, offset, size, ecryptfs_file_size);
313 while (pos < (offset + size)) {
314 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
315 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
316 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
317 size_t total_remaining_bytes = ((offset + size) - pos);
319 if (num_bytes > total_remaining_bytes)
320 num_bytes = total_remaining_bytes;
321 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
323 if (IS_ERR(ecryptfs_page)) {
324 rc = PTR_ERR(ecryptfs_page);
325 printk(KERN_ERR "%s: Error getting page at "
326 "index [%ld] from eCryptfs inode "
327 "mapping; rc = [%d]\n", __func__,
328 ecryptfs_page_idx, rc);
331 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
332 memcpy((data + data_offset),
333 ((char *)ecryptfs_page_virt + start_offset_in_page),
335 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
336 flush_dcache_page(ecryptfs_page);
337 SetPageUptodate(ecryptfs_page);
338 unlock_page(ecryptfs_page);
339 page_cache_release(ecryptfs_page);
341 data_offset += num_bytes;