1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Utility functions for file contents encryption/decryption on
4 * block device-based filesystems.
5 *
6 * Copyright (C) 2015, Google, Inc.
7 * Copyright (C) 2015, Motorola Mobility
8 */
9
10 #include <linux/pagemap.h>
11 #include <linux/module.h>
12 #include <linux/bio.h>
13 #include <linux/namei.h>
14 #include "fscrypt_private.h"
15
16 /**
17 * fscrypt_decrypt_bio() - decrypt the contents of a bio
18 * @bio: the bio to decrypt
19 *
20 * Decrypt the contents of a "read" bio following successful completion of the
21 * underlying disk read. The bio must be reading a whole number of blocks of an
22 * encrypted file directly into the page cache. If the bio is reading the
23 * ciphertext into bounce pages instead of the page cache (for example, because
24 * the file is also compressed, so decompression is required after decryption),
25 * then this function isn't applicable. This function may sleep, so it must be
26 * called from a workqueue rather than from the bio's bi_end_io callback.
27 *
28 * This function sets PG_error on any pages that contain any blocks that failed
29 * to be decrypted. The filesystem must not mark such pages uptodate.
30 */
fscrypt_decrypt_bio(struct bio * bio)31 void fscrypt_decrypt_bio(struct bio *bio)
32 {
33 struct bio_vec *bv;
34 struct bvec_iter_all iter_all;
35
36 bio_for_each_segment_all(bv, bio, iter_all) {
37 struct page *page = bv->bv_page;
38 int ret = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len,
39 bv->bv_offset);
40 if (ret)
41 SetPageError(page);
42 }
43 }
44 EXPORT_SYMBOL(fscrypt_decrypt_bio);
45
fscrypt_zeroout_range_inline_crypt(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)46 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
47 pgoff_t lblk, sector_t pblk,
48 unsigned int len)
49 {
50 const unsigned int blockbits = inode->i_blkbits;
51 const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
52 struct bio *bio;
53 int ret, err = 0;
54 int num_pages = 0;
55
56 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
57 bio = bio_alloc(GFP_NOFS, BIO_MAX_VECS);
58
59 while (len) {
60 unsigned int blocks_this_page = min(len, blocks_per_page);
61 unsigned int bytes_this_page = blocks_this_page << blockbits;
62
63 if (num_pages == 0) {
64 fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
65 bio_set_dev(bio, inode->i_sb->s_bdev);
66 bio->bi_iter.bi_sector =
67 pblk << (blockbits - SECTOR_SHIFT);
68 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
69 }
70 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
71 if (WARN_ON(ret != bytes_this_page)) {
72 err = -EIO;
73 goto out;
74 }
75 num_pages++;
76 len -= blocks_this_page;
77 lblk += blocks_this_page;
78 pblk += blocks_this_page;
79 if (num_pages == BIO_MAX_VECS || !len ||
80 !fscrypt_mergeable_bio(bio, inode, lblk)) {
81 err = submit_bio_wait(bio);
82 if (err)
83 goto out;
84 bio_reset(bio);
85 num_pages = 0;
86 }
87 }
88 out:
89 bio_put(bio);
90 return err;
91 }
92
93 /**
94 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
95 * @inode: the file's inode
96 * @lblk: the first file logical block to zero out
97 * @pblk: the first filesystem physical block to zero out
98 * @len: number of blocks to zero out
99 *
100 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
101 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
102 * both logically and physically contiguous. It's also assumed that the
103 * filesystem only uses a single block device, ->s_bdev.
104 *
105 * Note that since each block uses a different IV, this involves writing a
106 * different ciphertext to each block; we can't simply reuse the same one.
107 *
108 * Return: 0 on success; -errno on failure.
109 */
fscrypt_zeroout_range(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)110 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
111 sector_t pblk, unsigned int len)
112 {
113 const unsigned int blockbits = inode->i_blkbits;
114 const unsigned int blocksize = 1 << blockbits;
115 const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
116 const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
117 struct page *pages[16]; /* write up to 16 pages at a time */
118 unsigned int nr_pages;
119 unsigned int i;
120 unsigned int offset;
121 struct bio *bio;
122 int ret, err;
123
124 if (len == 0)
125 return 0;
126
127 if (fscrypt_inode_uses_inline_crypto(inode))
128 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,
129 len);
130
131 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);
132 nr_pages = min_t(unsigned int, ARRAY_SIZE(pages),
133 (len + blocks_per_page - 1) >> blocks_per_page_bits);
134
135 /*
136 * We need at least one page for ciphertext. Allocate the first one
137 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
138 *
139 * Any additional page allocations are allowed to fail, as they only
140 * help performance, and waiting on the mempool for them could deadlock.
141 */
142 for (i = 0; i < nr_pages; i++) {
143 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
144 GFP_NOWAIT | __GFP_NOWARN);
145 if (!pages[i])
146 break;
147 }
148 nr_pages = i;
149 if (WARN_ON(nr_pages <= 0))
150 return -EINVAL;
151
152 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
153 bio = bio_alloc(GFP_NOFS, nr_pages);
154
155 do {
156 bio_set_dev(bio, inode->i_sb->s_bdev);
157 bio->bi_iter.bi_sector = pblk << (blockbits - 9);
158 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
159
160 i = 0;
161 offset = 0;
162 do {
163 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
164 ZERO_PAGE(0), pages[i],
165 blocksize, offset, GFP_NOFS);
166 if (err)
167 goto out;
168 lblk++;
169 pblk++;
170 len--;
171 offset += blocksize;
172 if (offset == PAGE_SIZE || len == 0) {
173 ret = bio_add_page(bio, pages[i++], offset, 0);
174 if (WARN_ON(ret != offset)) {
175 err = -EIO;
176 goto out;
177 }
178 offset = 0;
179 }
180 } while (i != nr_pages && len != 0);
181
182 err = submit_bio_wait(bio);
183 if (err)
184 goto out;
185 bio_reset(bio);
186 } while (len != 0);
187 err = 0;
188 out:
189 bio_put(bio);
190 for (i = 0; i < nr_pages; i++)
191 fscrypt_free_bounce_page(pages[i]);
192 return err;
193 }
194 EXPORT_SYMBOL(fscrypt_zeroout_range);
195