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 * Return: %true on success; %false on failure. On failure, bio->bi_status is
29 * also set to an error status.
30 */
fscrypt_decrypt_bio(struct bio * bio)31 bool 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 err = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len,
39 bv->bv_offset);
40
41 if (err) {
42 bio->bi_status = errno_to_blk_status(err);
43 return false;
44 }
45 }
46 return true;
47 }
48 EXPORT_SYMBOL(fscrypt_decrypt_bio);
49
fscrypt_zeroout_range_inline_crypt(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)50 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
51 pgoff_t lblk, sector_t pblk,
52 unsigned int len)
53 {
54 const unsigned int blockbits = inode->i_blkbits;
55 const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
56 struct bio *bio;
57 int ret, err = 0;
58 int num_pages = 0;
59
60 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
61 bio = bio_alloc(GFP_NOFS, BIO_MAX_VECS);
62
63 while (len) {
64 unsigned int blocks_this_page = min(len, blocks_per_page);
65 unsigned int bytes_this_page = blocks_this_page << blockbits;
66
67 if (num_pages == 0) {
68 fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
69 bio_set_dev(bio, inode->i_sb->s_bdev);
70 bio->bi_iter.bi_sector =
71 pblk << (blockbits - SECTOR_SHIFT);
72 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
73 }
74 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
75 if (WARN_ON_ONCE(ret != bytes_this_page)) {
76 err = -EIO;
77 goto out;
78 }
79 num_pages++;
80 len -= blocks_this_page;
81 lblk += blocks_this_page;
82 pblk += blocks_this_page;
83 if (num_pages == BIO_MAX_VECS || !len ||
84 !fscrypt_mergeable_bio(bio, inode, lblk)) {
85 err = submit_bio_wait(bio);
86 if (err)
87 goto out;
88 bio_reset(bio);
89 num_pages = 0;
90 }
91 }
92 out:
93 bio_put(bio);
94 return err;
95 }
96
97 /**
98 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
99 * @inode: the file's inode
100 * @lblk: the first file logical block to zero out
101 * @pblk: the first filesystem physical block to zero out
102 * @len: number of blocks to zero out
103 *
104 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
105 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
106 * both logically and physically contiguous. It's also assumed that the
107 * filesystem only uses a single block device, ->s_bdev.
108 *
109 * Note that since each block uses a different IV, this involves writing a
110 * different ciphertext to each block; we can't simply reuse the same one.
111 *
112 * Return: 0 on success; -errno on failure.
113 */
fscrypt_zeroout_range(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)114 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
115 sector_t pblk, unsigned int len)
116 {
117 const struct fscrypt_info *ci = inode->i_crypt_info;
118 const unsigned int du_bits = ci->ci_data_unit_bits;
119 const unsigned int du_size = 1U << du_bits;
120 const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits;
121 const unsigned int du_per_page = 1U << du_per_page_bits;
122 u64 du_index = (u64)lblk << (inode->i_blkbits - du_bits);
123 u64 du_remaining = (u64)len << (inode->i_blkbits - du_bits);
124 sector_t sector = pblk << (inode->i_blkbits - SECTOR_SHIFT);
125 struct page *pages[16]; /* write up to 16 pages at a time */
126 unsigned int nr_pages;
127 unsigned int i;
128 unsigned int offset;
129 struct bio *bio;
130 int ret, err;
131
132 if (len == 0)
133 return 0;
134
135 if (fscrypt_inode_uses_inline_crypto(inode))
136 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,
137 len);
138
139 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);
140 nr_pages = min_t(u64, ARRAY_SIZE(pages),
141 (du_remaining + du_per_page - 1) >> du_per_page_bits);
142
143 /*
144 * We need at least one page for ciphertext. Allocate the first one
145 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
146 *
147 * Any additional page allocations are allowed to fail, as they only
148 * help performance, and waiting on the mempool for them could deadlock.
149 */
150 for (i = 0; i < nr_pages; i++) {
151 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
152 GFP_NOWAIT | __GFP_NOWARN);
153 if (!pages[i])
154 break;
155 }
156 nr_pages = i;
157 if (WARN_ON_ONCE(nr_pages <= 0))
158 return -EINVAL;
159
160 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
161 bio = bio_alloc(GFP_NOFS, nr_pages);
162
163 do {
164 bio_set_dev(bio, inode->i_sb->s_bdev);
165 bio->bi_iter.bi_sector = sector;
166 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
167
168 i = 0;
169 offset = 0;
170 do {
171 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, du_index,
172 ZERO_PAGE(0), pages[i],
173 du_size, offset,
174 GFP_NOFS);
175 if (err)
176 goto out;
177 du_index++;
178 sector += 1U << (du_bits - SECTOR_SHIFT);
179 du_remaining--;
180 offset += du_size;
181 if (offset == PAGE_SIZE || du_remaining == 0) {
182 ret = bio_add_page(bio, pages[i++], offset, 0);
183 if (WARN_ON_ONCE(ret != offset)) {
184 err = -EIO;
185 goto out;
186 }
187 offset = 0;
188 }
189 } while (i != nr_pages && du_remaining != 0);
190
191 err = submit_bio_wait(bio);
192 if (err)
193 goto out;
194 bio_reset(bio);
195 } while (du_remaining != 0);
196 err = 0;
197 out:
198 bio_put(bio);
199 for (i = 0; i < nr_pages; i++)
200 fscrypt_free_bounce_page(pages[i]);
201 return err;
202 }
203 EXPORT_SYMBOL(fscrypt_zeroout_range);
204