1 /**
2 * eCryptfs: Linux filesystem encryption layer
3 *
4 * Copyright (C) 2007 International Business Machines Corp.
5 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
6 *
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.
11 *
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.
16 *
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
20 * 02111-1307, USA.
21 */
22
23 #include <linux/fs.h>
24 #include <linux/pagemap.h>
25 #include "ecryptfs_kernel.h"
26
27 /**
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
33 * file
34 *
35 * Write data to the lower file.
36 *
37 * Returns bytes written on success; less than zero on error
38 */
ecryptfs_write_lower(struct inode * ecryptfs_inode,char * data,loff_t offset,size_t size)39 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
40 loff_t offset, size_t size)
41 {
42 struct file *lower_file;
43 mm_segment_t fs_save;
44 ssize_t rc;
45
46 lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
47 if (!lower_file)
48 return -EIO;
49 fs_save = get_fs();
50 set_fs(get_ds());
51 rc = vfs_write(lower_file, data, size, &offset);
52 set_fs(fs_save);
53 mark_inode_dirty_sync(ecryptfs_inode);
54 return rc;
55 }
56
57 /**
58 * ecryptfs_write_lower_page_segment
59 * @ecryptfs_inode: The eCryptfs inode
60 * @page_for_lower: The page containing the data to be written to the
61 * lower file
62 * @offset_in_page: The offset in the @page_for_lower from which to
63 * start writing the data
64 * @size: The amount of data from @page_for_lower to write to the
65 * lower file
66 *
67 * Determines the byte offset in the file for the given page and
68 * offset within the page, maps the page, and makes the call to write
69 * the contents of @page_for_lower to the lower inode.
70 *
71 * Returns zero on success; non-zero otherwise
72 */
ecryptfs_write_lower_page_segment(struct inode * ecryptfs_inode,struct page * page_for_lower,size_t offset_in_page,size_t size)73 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
74 struct page *page_for_lower,
75 size_t offset_in_page, size_t size)
76 {
77 char *virt;
78 loff_t offset;
79 int rc;
80
81 offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
82 + offset_in_page);
83 virt = kmap(page_for_lower);
84 rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
85 if (rc > 0)
86 rc = 0;
87 kunmap(page_for_lower);
88 return rc;
89 }
90
91 /**
92 * ecryptfs_write
93 * @ecryptfs_inode: The eCryptfs file into which to write
94 * @data: Virtual address where data to write is located
95 * @offset: Offset in the eCryptfs file at which to begin writing the
96 * data from @data
97 * @size: The number of bytes to write from @data
98 *
99 * Write an arbitrary amount of data to an arbitrary location in the
100 * eCryptfs inode page cache. This is done on a page-by-page, and then
101 * by an extent-by-extent, basis; individual extents are encrypted and
102 * written to the lower page cache (via VFS writes). This function
103 * takes care of all the address translation to locations in the lower
104 * filesystem; it also handles truncate events, writing out zeros
105 * where necessary.
106 *
107 * Returns zero on success; non-zero otherwise
108 */
ecryptfs_write(struct inode * ecryptfs_inode,char * data,loff_t offset,size_t size)109 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
110 size_t size)
111 {
112 struct page *ecryptfs_page;
113 struct ecryptfs_crypt_stat *crypt_stat;
114 char *ecryptfs_page_virt;
115 loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
116 loff_t data_offset = 0;
117 loff_t pos;
118 int rc = 0;
119
120 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
121 /*
122 * if we are writing beyond current size, then start pos
123 * at the current size - we'll fill in zeros from there.
124 */
125 if (offset > ecryptfs_file_size)
126 pos = ecryptfs_file_size;
127 else
128 pos = offset;
129 while (pos < (offset + size)) {
130 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
131 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
132 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
133 loff_t total_remaining_bytes = ((offset + size) - pos);
134
135 if (fatal_signal_pending(current)) {
136 rc = -EINTR;
137 break;
138 }
139
140 if (num_bytes > total_remaining_bytes)
141 num_bytes = total_remaining_bytes;
142 if (pos < offset) {
143 /* remaining zeros to write, up to destination offset */
144 loff_t total_remaining_zeros = (offset - pos);
145
146 if (num_bytes > total_remaining_zeros)
147 num_bytes = total_remaining_zeros;
148 }
149 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
150 ecryptfs_page_idx);
151 if (IS_ERR(ecryptfs_page)) {
152 rc = PTR_ERR(ecryptfs_page);
153 printk(KERN_ERR "%s: Error getting page at "
154 "index [%ld] from eCryptfs inode "
155 "mapping; rc = [%d]\n", __func__,
156 ecryptfs_page_idx, rc);
157 goto out;
158 }
159 ecryptfs_page_virt = kmap_atomic(ecryptfs_page);
160
161 /*
162 * pos: where we're now writing, offset: where the request was
163 * If current pos is before request, we are filling zeros
164 * If we are at or beyond request, we are writing the *data*
165 * If we're in a fresh page beyond eof, zero it in either case
166 */
167 if (pos < offset || !start_offset_in_page) {
168 /* We are extending past the previous end of the file.
169 * Fill in zero values to the end of the page */
170 memset(((char *)ecryptfs_page_virt
171 + start_offset_in_page), 0,
172 PAGE_CACHE_SIZE - start_offset_in_page);
173 }
174
175 /* pos >= offset, we are now writing the data request */
176 if (pos >= offset) {
177 memcpy(((char *)ecryptfs_page_virt
178 + start_offset_in_page),
179 (data + data_offset), num_bytes);
180 data_offset += num_bytes;
181 }
182 kunmap_atomic(ecryptfs_page_virt);
183 flush_dcache_page(ecryptfs_page);
184 SetPageUptodate(ecryptfs_page);
185 unlock_page(ecryptfs_page);
186 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
187 rc = ecryptfs_encrypt_page(ecryptfs_page);
188 else
189 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
190 ecryptfs_page,
191 start_offset_in_page,
192 data_offset);
193 page_cache_release(ecryptfs_page);
194 if (rc) {
195 printk(KERN_ERR "%s: Error encrypting "
196 "page; rc = [%d]\n", __func__, rc);
197 goto out;
198 }
199 pos += num_bytes;
200 }
201 if (pos > ecryptfs_file_size) {
202 i_size_write(ecryptfs_inode, pos);
203 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
204 int rc2;
205
206 rc2 = ecryptfs_write_inode_size_to_metadata(
207 ecryptfs_inode);
208 if (rc2) {
209 printk(KERN_ERR "Problem with "
210 "ecryptfs_write_inode_size_to_metadata; "
211 "rc = [%d]\n", rc2);
212 if (!rc)
213 rc = rc2;
214 goto out;
215 }
216 }
217 }
218 out:
219 return rc;
220 }
221
222 /**
223 * ecryptfs_read_lower
224 * @data: The read data is stored here by this function
225 * @offset: Byte offset in the lower file from which to read the data
226 * @size: Number of bytes to read from @offset of the lower file and
227 * store into @data
228 * @ecryptfs_inode: The eCryptfs inode
229 *
230 * Read @size bytes of data at byte offset @offset from the lower
231 * inode into memory location @data.
232 *
233 * Returns bytes read on success; 0 on EOF; less than zero on error
234 */
ecryptfs_read_lower(char * data,loff_t offset,size_t size,struct inode * ecryptfs_inode)235 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
236 struct inode *ecryptfs_inode)
237 {
238 struct file *lower_file;
239 mm_segment_t fs_save;
240 ssize_t rc;
241
242 lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
243 if (!lower_file)
244 return -EIO;
245 fs_save = get_fs();
246 set_fs(get_ds());
247 rc = vfs_read(lower_file, data, size, &offset);
248 set_fs(fs_save);
249 return rc;
250 }
251
252 /**
253 * ecryptfs_read_lower_page_segment
254 * @page_for_ecryptfs: The page into which data for eCryptfs will be
255 * written
256 * @offset_in_page: Offset in @page_for_ecryptfs from which to start
257 * writing
258 * @size: The number of bytes to write into @page_for_ecryptfs
259 * @ecryptfs_inode: The eCryptfs inode
260 *
261 * Determines the byte offset in the file for the given page and
262 * offset within the page, maps the page, and makes the call to read
263 * the contents of @page_for_ecryptfs from the lower inode.
264 *
265 * Returns zero on success; non-zero otherwise
266 */
ecryptfs_read_lower_page_segment(struct page * page_for_ecryptfs,pgoff_t page_index,size_t offset_in_page,size_t size,struct inode * ecryptfs_inode)267 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
268 pgoff_t page_index,
269 size_t offset_in_page, size_t size,
270 struct inode *ecryptfs_inode)
271 {
272 char *virt;
273 loff_t offset;
274 int rc;
275
276 offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
277 virt = kmap(page_for_ecryptfs);
278 rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
279 if (rc > 0)
280 rc = 0;
281 kunmap(page_for_ecryptfs);
282 flush_dcache_page(page_for_ecryptfs);
283 return rc;
284 }
285