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 */
27int 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 */
57int 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_local_page(page_for_lower);
68	rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
69	if (rc > 0)
70		rc = 0;
71	kunmap_local(virt);
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 */
93int 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_local_page(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_local(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	}
202out:
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 */
219int 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 * @page_index: Page index in @page_for_ecryptfs from which to start
234 *		writing
235 * @offset_in_page: Offset in @page_for_ecryptfs from which to start
236 *                  writing
237 * @size: The number of bytes to write into @page_for_ecryptfs
238 * @ecryptfs_inode: The eCryptfs inode
239 *
240 * Determines the byte offset in the file for the given page and
241 * offset within the page, maps the page, and makes the call to read
242 * the contents of @page_for_ecryptfs from the lower inode.
243 *
244 * Returns zero on success; non-zero otherwise
245 */
246int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
247				     pgoff_t page_index,
248				     size_t offset_in_page, size_t size,
249				     struct inode *ecryptfs_inode)
250{
251	char *virt;
252	loff_t offset;
253	int rc;
254
255	offset = ((((loff_t)page_index) << PAGE_SHIFT) + offset_in_page);
256	virt = kmap_local_page(page_for_ecryptfs);
257	rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
258	if (rc > 0)
259		rc = 0;
260	kunmap_local(virt);
261	flush_dcache_page(page_for_ecryptfs);
262	return rc;
263}
264