1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /**
3 * eCryptfs: Linux filesystem encryption layer
4 *
5 * Copyright (C) 2007 International Business Machines Corp.
6 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
7 */
8
9 #include <linux/fs.h>
10 #include <linux/pagemap.h>
11 #include <linux/sched/signal.h>
12
13 #include "ecryptfs_kernel.h"
14
15 /**
16 * ecryptfs_write_lower
17 * @ecryptfs_inode: The eCryptfs inode
18 * @data: Data to write
19 * @offset: Byte offset in the lower file to which to write the data
20 * @size: Number of bytes from @data to write at @offset in the lower
21 * file
22 *
23 * Write data to the lower file.
24 *
25 * Returns bytes written on success; less than zero on error
26 */
27 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
28 loff_t offset, size_t size)
29 {
30 struct file *lower_file;
31 ssize_t rc;
32
33 lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
34 if (!lower_file)
35 return -EIO;
36 rc = kernel_write(lower_file, data, size, &offset);
37 mark_inode_dirty_sync(ecryptfs_inode);
38 return rc;
39 }
40
41 /**
42 * ecryptfs_write_lower_page_segment
43 * @ecryptfs_inode: The eCryptfs inode
44 * @page_for_lower: The page containing the data to be written to the
45 * lower file
46 * @offset_in_page: The offset in the @page_for_lower from which to
47 * start writing the data
48 * @size: The amount of data from @page_for_lower to write to the
49 * lower file
50 *
51 * Determines the byte offset in the file for the given page and
52 * offset within the page, maps the page, and makes the call to write
53 * the contents of @page_for_lower to the lower inode.
54 *
55 * Returns zero on success; non-zero otherwise
56 */
57 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
58 struct page *page_for_lower,
59 size_t offset_in_page, size_t size)
60 {
61 char *virt;
62 loff_t offset;
63 int rc;
64
65 offset = ((((loff_t)page_for_lower->index) << PAGE_SHIFT)
66 + offset_in_page);
67 virt = kmap(page_for_lower);
68 rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
69 if (rc > 0)
70 rc = 0;
71 kunmap(page_for_lower);
72 return rc;
73 }
74
75 /**
76 * ecryptfs_write
77 * @ecryptfs_inode: The eCryptfs file into which to write
78 * @data: Virtual address where data to write is located
79 * @offset: Offset in the eCryptfs file at which to begin writing the
80 * data from @data
81 * @size: The number of bytes to write from @data
82 *
83 * Write an arbitrary amount of data to an arbitrary location in the
84 * eCryptfs inode page cache. This is done on a page-by-page, and then
85 * by an extent-by-extent, basis; individual extents are encrypted and
86 * written to the lower page cache (via VFS writes). This function
87 * takes care of all the address translation to locations in the lower
88 * filesystem; it also handles truncate events, writing out zeros
89 * where necessary.
90 *
91 * Returns zero on success; non-zero otherwise
92 */
93 int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
94 size_t size)
95 {
96 struct page *ecryptfs_page;
97 struct ecryptfs_crypt_stat *crypt_stat;
98 char *ecryptfs_page_virt;
99 loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
100 loff_t data_offset = 0;
101 loff_t pos;
102 int rc = 0;
103
104 crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
105 /*
106 * if we are writing beyond current size, then start pos
107 * at the current size - we'll fill in zeros from there.
108 */
109 if (offset > ecryptfs_file_size)
110 pos = ecryptfs_file_size;
111 else
112 pos = offset;
113 while (pos < (offset + size)) {
114 pgoff_t ecryptfs_page_idx = (pos >> PAGE_SHIFT);
115 size_t start_offset_in_page = (pos & ~PAGE_MASK);
116 size_t num_bytes = (PAGE_SIZE - start_offset_in_page);
117 loff_t total_remaining_bytes = ((offset + size) - pos);
118
119 if (fatal_signal_pending(current)) {
120 rc = -EINTR;
121 break;
122 }
123
124 if (num_bytes > total_remaining_bytes)
125 num_bytes = total_remaining_bytes;
126 if (pos < offset) {
127 /* remaining zeros to write, up to destination offset */
128 loff_t total_remaining_zeros = (offset - pos);
129
130 if (num_bytes > total_remaining_zeros)
131 num_bytes = total_remaining_zeros;
132 }
133 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
134 ecryptfs_page_idx);
135 if (IS_ERR(ecryptfs_page)) {
136 rc = PTR_ERR(ecryptfs_page);
137 printk(KERN_ERR "%s: Error getting page at "
138 "index [%ld] from eCryptfs inode "
139 "mapping; rc = [%d]\n", __func__,
140 ecryptfs_page_idx, rc);
141 goto out;
142 }
143 ecryptfs_page_virt = kmap_atomic(ecryptfs_page);
144
145 /*
146 * pos: where we're now writing, offset: where the request was
147 * If current pos is before request, we are filling zeros
148 * If we are at or beyond request, we are writing the *data*
149 * If we're in a fresh page beyond eof, zero it in either case
150 */
151 if (pos < offset || !start_offset_in_page) {
152 /* We are extending past the previous end of the file.
153 * Fill in zero values to the end of the page */
154 memset(((char *)ecryptfs_page_virt
155 + start_offset_in_page), 0,
156 PAGE_SIZE - start_offset_in_page);
157 }
158
159 /* pos >= offset, we are now writing the data request */
160 if (pos >= offset) {
161 memcpy(((char *)ecryptfs_page_virt
162 + start_offset_in_page),
163 (data + data_offset), num_bytes);
164 data_offset += num_bytes;
165 }
166 kunmap_atomic(ecryptfs_page_virt);
167 flush_dcache_page(ecryptfs_page);
168 SetPageUptodate(ecryptfs_page);
169 unlock_page(ecryptfs_page);
170 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
171 rc = ecryptfs_encrypt_page(ecryptfs_page);
172 else
173 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
174 ecryptfs_page,
175 start_offset_in_page,
176 data_offset);
177 put_page(ecryptfs_page);
178 if (rc) {
179 printk(KERN_ERR "%s: Error encrypting "
180 "page; rc = [%d]\n", __func__, rc);
181 goto out;
182 }
183 pos += num_bytes;
184 }
185 if (pos > ecryptfs_file_size) {
186 i_size_write(ecryptfs_inode, pos);
187 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
188 int rc2;
189
190 rc2 = ecryptfs_write_inode_size_to_metadata(
191 ecryptfs_inode);
192 if (rc2) {
193 printk(KERN_ERR "Problem with "
194 "ecryptfs_write_inode_size_to_metadata; "
195 "rc = [%d]\n", rc2);
196 if (!rc)
197 rc = rc2;
198 goto out;
199 }
200 }
201 }
202 out:
203 return rc;
204 }
205
206 /**
207 * ecryptfs_read_lower
208 * @data: The read data is stored here by this function
209 * @offset: Byte offset in the lower file from which to read the data
210 * @size: Number of bytes to read from @offset of the lower file and
211 * store into @data
212 * @ecryptfs_inode: The eCryptfs inode
213 *
214 * Read @size bytes of data at byte offset @offset from the lower
215 * inode into memory location @data.
216 *
217 * Returns bytes read on success; 0 on EOF; less than zero on error
218 */
219 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
220 struct inode *ecryptfs_inode)
221 {
222 struct file *lower_file;
223 lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
224 if (!lower_file)
225 return -EIO;
226 return kernel_read(lower_file, data, size, &offset);
227 }
228
229 /**
230 * ecryptfs_read_lower_page_segment
231 * @page_for_ecryptfs: The page into which data for eCryptfs will be
232 * written
233 * @offset_in_page: Offset in @page_for_ecryptfs from which to start
234 * writing
235 * @size: The number of bytes to write into @page_for_ecryptfs
236 * @ecryptfs_inode: The eCryptfs inode
237 *
238 * Determines the byte offset in the file for the given page and
239 * offset within the page, maps the page, and makes the call to read
240 * the contents of @page_for_ecryptfs from the lower inode.
241 *
242 * Returns zero on success; non-zero otherwise
243 */
244 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
245 pgoff_t page_index,
246 size_t offset_in_page, size_t size,
247 struct inode *ecryptfs_inode)
248 {
249 char *virt;
250 loff_t offset;
251 int rc;
252
253 offset = ((((loff_t)page_index) << PAGE_SHIFT) + offset_in_page);
254 virt = kmap(page_for_ecryptfs);
255 rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
256 if (rc > 0)
257 rc = 0;
258 kunmap(page_for_ecryptfs);
259 flush_dcache_page(page_for_ecryptfs);
260 return rc;
261 }