1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * This contains encryption functions for per-file encryption.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility
7 *
8 * Written by Michael Halcrow, 2014.
9 *
10 * Filename encryption additions
11 * Uday Savagaonkar, 2014
12 * Encryption policy handling additions
13 * Ildar Muslukhov, 2014
14 * Add fscrypt_pullback_bio_page()
15 * Jaegeuk Kim, 2015.
16 *
17 * This has not yet undergone a rigorous security audit.
18 *
19 * The usage of AES-XTS should conform to recommendations in NIST
20 * Special Publication 800-38E and IEEE P1619/D16.
21 */
22
23 #include <linux/pagemap.h>
24 #include <linux/module.h>
25 #include <linux/bio.h>
26 #include <linux/namei.h>
27 #include "fscrypt_private.h"
28
fscrypt_decrypt_bio(struct bio * bio)29 void fscrypt_decrypt_bio(struct bio *bio)
30 {
31 struct bio_vec *bv;
32 struct bvec_iter_all iter_all;
33
34 bio_for_each_segment_all(bv, bio, iter_all) {
35 struct page *page = bv->bv_page;
36 int ret = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len,
37 bv->bv_offset);
38 if (ret)
39 SetPageError(page);
40 }
41 }
42 EXPORT_SYMBOL(fscrypt_decrypt_bio);
43
fscrypt_zeroout_range_inline_crypt(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)44 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
45 pgoff_t lblk, sector_t pblk,
46 unsigned int len)
47 {
48 const unsigned int blockbits = inode->i_blkbits;
49 const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
50 struct bio *bio;
51 int ret, err = 0;
52 int num_pages = 0;
53
54 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
55 bio = bio_alloc(GFP_NOFS, BIO_MAX_VECS);
56
57 while (len) {
58 unsigned int blocks_this_page = min(len, blocks_per_page);
59 unsigned int bytes_this_page = blocks_this_page << blockbits;
60
61 if (num_pages == 0) {
62 fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
63 bio_set_dev(bio, inode->i_sb->s_bdev);
64 bio->bi_iter.bi_sector =
65 pblk << (blockbits - SECTOR_SHIFT);
66 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
67 }
68 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
69 if (WARN_ON(ret != bytes_this_page)) {
70 err = -EIO;
71 goto out;
72 }
73 num_pages++;
74 len -= blocks_this_page;
75 lblk += blocks_this_page;
76 pblk += blocks_this_page;
77 if (num_pages == BIO_MAX_VECS || !len ||
78 !fscrypt_mergeable_bio(bio, inode, lblk)) {
79 err = submit_bio_wait(bio);
80 if (err)
81 goto out;
82 bio_reset(bio);
83 num_pages = 0;
84 }
85 }
86 out:
87 bio_put(bio);
88 return err;
89 }
90
91 /**
92 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
93 * @inode: the file's inode
94 * @lblk: the first file logical block to zero out
95 * @pblk: the first filesystem physical block to zero out
96 * @len: number of blocks to zero out
97 *
98 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
99 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
100 * both logically and physically contiguous. It's also assumed that the
101 * filesystem only uses a single block device, ->s_bdev.
102 *
103 * Note that since each block uses a different IV, this involves writing a
104 * different ciphertext to each block; we can't simply reuse the same one.
105 *
106 * Return: 0 on success; -errno on failure.
107 */
fscrypt_zeroout_range(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)108 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
109 sector_t pblk, unsigned int len)
110 {
111 const unsigned int blockbits = inode->i_blkbits;
112 const unsigned int blocksize = 1 << blockbits;
113 const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
114 const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
115 struct page *pages[16]; /* write up to 16 pages at a time */
116 unsigned int nr_pages;
117 unsigned int i;
118 unsigned int offset;
119 struct bio *bio;
120 int ret, err;
121
122 if (len == 0)
123 return 0;
124
125 if (fscrypt_inode_uses_inline_crypto(inode))
126 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,
127 len);
128
129 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);
130 nr_pages = min_t(unsigned int, ARRAY_SIZE(pages),
131 (len + blocks_per_page - 1) >> blocks_per_page_bits);
132
133 /*
134 * We need at least one page for ciphertext. Allocate the first one
135 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
136 *
137 * Any additional page allocations are allowed to fail, as they only
138 * help performance, and waiting on the mempool for them could deadlock.
139 */
140 for (i = 0; i < nr_pages; i++) {
141 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
142 GFP_NOWAIT | __GFP_NOWARN);
143 if (!pages[i])
144 break;
145 }
146 nr_pages = i;
147 if (WARN_ON(nr_pages <= 0))
148 return -EINVAL;
149
150 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
151 bio = bio_alloc(GFP_NOFS, nr_pages);
152
153 do {
154 bio_set_dev(bio, inode->i_sb->s_bdev);
155 bio->bi_iter.bi_sector = pblk << (blockbits - 9);
156 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
157
158 i = 0;
159 offset = 0;
160 do {
161 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
162 ZERO_PAGE(0), pages[i],
163 blocksize, offset, GFP_NOFS);
164 if (err)
165 goto out;
166 lblk++;
167 pblk++;
168 len--;
169 offset += blocksize;
170 if (offset == PAGE_SIZE || len == 0) {
171 ret = bio_add_page(bio, pages[i++], offset, 0);
172 if (WARN_ON(ret != offset)) {
173 err = -EIO;
174 goto out;
175 }
176 offset = 0;
177 }
178 } while (i != nr_pages && len != 0);
179
180 err = submit_bio_wait(bio);
181 if (err)
182 goto out;
183 bio_reset(bio);
184 } while (len != 0);
185 err = 0;
186 out:
187 bio_put(bio);
188 for (i = 0; i < nr_pages; i++)
189 fscrypt_free_bounce_page(pages[i]);
190 return err;
191 }
192 EXPORT_SYMBOL(fscrypt_zeroout_range);
193