summaryrefslogtreecommitdiffstats
path: root/fs/ecryptfs/read_write.c
blob: 158a3a39f82de76a916ba7fb1edf680cf4184d8f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
/**
 * eCryptfs: Linux filesystem encryption layer
 *
 * Copyright (C) 2007 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <linux/fs.h>
#include <linux/pagemap.h>
#include "ecryptfs_kernel.h"

/**
 * ecryptfs_write_lower
 * @ecryptfs_inode: The eCryptfs inode
 * @data: Data to write
 * @offset: Byte offset in the lower file to which to write the data
 * @size: Number of bytes from @data to write at @offset in the lower
 *        file
 *
 * Write data to the lower file.
 *
 * Returns bytes written on success; less than zero on error
 */
int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
			 loff_t offset, size_t size)
{
	struct file *lower_file;
	ssize_t rc;

	lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
	if (!lower_file)
		return -EIO;
	rc = kernel_write(lower_file, data, size, offset);
	mark_inode_dirty_sync(ecryptfs_inode);
	return rc;
}

/**
 * ecryptfs_write_lower_page_segment
 * @ecryptfs_inode: The eCryptfs inode
 * @page_for_lower: The page containing the data to be written to the
 *                  lower file
 * @offset_in_page: The offset in the @page_for_lower from which to
 *                  start writing the data
 * @size: The amount of data from @page_for_lower to write to the
 *        lower file
 *
 * Determines the byte offset in the file for the given page and
 * offset within the page, maps the page, and makes the call to write
 * the contents of @page_for_lower to the lower inode.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
				      struct page *page_for_lower,
				      size_t offset_in_page, size_t size)
{
	char *virt;
	loff_t offset;
	int rc;

	offset = ((((loff_t)page_for_lower->index) << PAGE_SHIFT)
		  + offset_in_page);
	virt = kmap(page_for_lower);
	rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
	if (rc > 0)
		rc = 0;
	kunmap(page_for_lower);
	return rc;
}

/**
 * ecryptfs_write
 * @ecryptfs_inode: The eCryptfs file into which to write
 * @data: Virtual address where data to write is located
 * @offset: Offset in the eCryptfs file at which to begin writing the
 *          data from @data
 * @size: The number of bytes to write from @data
 *
 * Write an arbitrary amount of data to an arbitrary location in the
 * eCryptfs inode page cache. This is done on a page-by-page, and then
 * by an extent-by-extent, basis; individual extents are encrypted and
 * written to the lower page cache (via VFS writes). This function
 * takes care of all the address translation to locations in the lower
 * filesystem; it also handles truncate events, writing out zeros
 * where necessary.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
		   size_t size)
{
	struct page *ecryptfs_page;
	struct ecryptfs_crypt_stat *crypt_stat;
	char *ecryptfs_page_virt;
	loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
	loff_t data_offset = 0;
	loff_t pos;
	int rc = 0;

	crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
	/*
	 * if we are writing beyond current size, then start pos
	 * at the current size - we'll fill in zeros from there.
	 */
	if (offset > ecryptfs_file_size)
		pos = ecryptfs_file_size;
	else
		pos = offset;
	while (pos < (offset + size)) {
		pgoff_t ecryptfs_page_idx = (pos >> PAGE_SHIFT);
		size_t start_offset_in_page = (pos & ~PAGE_MASK);
		size_t num_bytes = (PAGE_SIZE - start_offset_in_page);
		loff_t total_remaining_bytes = ((offset + size) - pos);

		if (fatal_signal_pending(current)) {
			rc = -EINTR;
			break;
		}

		if (num_bytes > total_remaining_bytes)
			num_bytes = total_remaining_bytes;
		if (pos < offset) {
			/* remaining zeros to write, up to destination offset */
			loff_t total_remaining_zeros = (offset - pos);

			if (num_bytes > total_remaining_zeros)
				num_bytes = total_remaining_zeros;
		}
		ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
							 ecryptfs_page_idx);
		if (IS_ERR(ecryptfs_page)) {
			rc = PTR_ERR(ecryptfs_page);
			printk(KERN_ERR "%s: Error getting page at "
			       "index [%ld] from eCryptfs inode "
			       "mapping; rc = [%d]\n", __func__,
			       ecryptfs_page_idx, rc);
			goto out;
		}
		ecryptfs_page_virt = kmap_atomic(ecryptfs_page);

		/*
		 * pos: where we're now writing, offset: where the request was
		 * If current pos is before request, we are filling zeros
		 * If we are at or beyond request, we are writing the *data*
		 * If we're in a fresh page beyond eof, zero it in either case
		 */
		if (pos < offset || !start_offset_in_page) {
			/* We are extending past the previous end of the file.
			 * Fill in zero values to the end of the page */
			memset(((char *)ecryptfs_page_virt
				+ start_offset_in_page), 0,
				PAGE_SIZE - start_offset_in_page);
		}

		/* pos >= offset, we are now writing the data request */
		if (pos >= offset) {
			memcpy(((char *)ecryptfs_page_virt
				+ start_offset_in_page),
			       (data + data_offset), num_bytes);
			data_offset += num_bytes;
		}
		kunmap_atomic(ecryptfs_page_virt);
		flush_dcache_page(ecryptfs_page);
		SetPageUptodate(ecryptfs_page);
		unlock_page(ecryptfs_page);
		if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
			rc = ecryptfs_encrypt_page(ecryptfs_page);
		else
			rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
						ecryptfs_page,
						start_offset_in_page,
						data_offset);
		put_page(ecryptfs_page);
		if (rc) {
			printk(KERN_ERR "%s: Error encrypting "
			       "page; rc = [%d]\n", __func__, rc);
			goto out;
		}
		pos += num_bytes;
	}
	if (pos > ecryptfs_file_size) {
		i_size_write(ecryptfs_inode, pos);
		if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
			int rc2;

			rc2 = ecryptfs_write_inode_size_to_metadata(
								ecryptfs_inode);
			if (rc2) {
				printk(KERN_ERR	"Problem with "
				       "ecryptfs_write_inode_size_to_metadata; "
				       "rc = [%d]\n", rc2);
				if (!rc)
					rc = rc2;
				goto out;
			}
		}
	}
out:
	return rc;
}

/**
 * ecryptfs_read_lower
 * @data: The read data is stored here by this function
 * @offset: Byte offset in the lower file from which to read the data
 * @size: Number of bytes to read from @offset of the lower file and
 *        store into @data
 * @ecryptfs_inode: The eCryptfs inode
 *
 * Read @size bytes of data at byte offset @offset from the lower
 * inode into memory location @data.
 *
 * Returns bytes read on success; 0 on EOF; less than zero on error
 */
int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
			struct inode *ecryptfs_inode)
{
	struct file *lower_file;
	lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
	if (!lower_file)
		return -EIO;
	return kernel_read(lower_file, offset, data, size);
}

/**
 * ecryptfs_read_lower_page_segment
 * @page_for_ecryptfs: The page into which data for eCryptfs will be
 *                     written
 * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 *                  writing
 * @size: The number of bytes to write into @page_for_ecryptfs
 * @ecryptfs_inode: The eCryptfs inode
 *
 * Determines the byte offset in the file for the given page and
 * offset within the page, maps the page, and makes the call to read
 * the contents of @page_for_ecryptfs from the lower inode.
 *
 * Returns zero on success; non-zero otherwise
 */
int 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)
{
	char *virt;
	loff_t offset;
	int rc;

	offset = ((((loff_t)page_index) << PAGE_SHIFT) + offset_in_page);
	virt = kmap(page_for_ecryptfs);
	rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
	if (rc > 0)
		rc = 0;
	kunmap(page_for_ecryptfs);
	flush_dcache_page(page_for_ecryptfs);
	return rc;
}
OpenPOWER on IntegriCloud