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 folio_iter fi;
34
35 bio_for_each_folio_all(fi, bio) {
36 int err = fscrypt_decrypt_pagecache_blocks(fi.folio, fi.length,
37 fi.offset);
38
39 if (err) {
40 bio->bi_status = errno_to_blk_status(err);
41 return false;
42 }
43 }
44 return true;
45 }
46 EXPORT_SYMBOL(fscrypt_decrypt_bio);
47
fscrypt_zeroout_range_inline_crypt(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)48 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
49 pgoff_t lblk, sector_t pblk,
50 unsigned int len)
51 {
52 const unsigned int blockbits = inode->i_blkbits;
53 const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
54 struct bio *bio;
55 int ret, err = 0;
56 int num_pages = 0;
57
58 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
59 bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,
60 GFP_NOFS);
61
62 while (len) {
63 unsigned int blocks_this_page = min(len, blocks_per_page);
64 unsigned int bytes_this_page = blocks_this_page << blockbits;
65
66 if (num_pages == 0) {
67 fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
68 bio->bi_iter.bi_sector =
69 pblk << (blockbits - SECTOR_SHIFT);
70 }
71 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
72 if (WARN_ON_ONCE(ret != bytes_this_page)) {
73 err = -EIO;
74 goto out;
75 }
76 num_pages++;
77 len -= blocks_this_page;
78 lblk += blocks_this_page;
79 pblk += blocks_this_page;
80 if (num_pages == BIO_MAX_VECS || !len ||
81 !fscrypt_mergeable_bio(bio, inode, lblk)) {
82 err = submit_bio_wait(bio);
83 if (err)
84 goto out;
85 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE);
86 num_pages = 0;
87 }
88 }
89 out:
90 bio_put(bio);
91 return err;
92 }
93
94 /**
95 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
96 * @inode: the file's inode
97 * @lblk: the first file logical block to zero out
98 * @pblk: the first filesystem physical block to zero out
99 * @len: number of blocks to zero out
100 *
101 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
102 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
103 * both logically and physically contiguous. It's also assumed that the
104 * filesystem only uses a single block device, ->s_bdev.
105 *
106 * Note that since each block uses a different IV, this involves writing a
107 * different ciphertext to each block; we can't simply reuse the same one.
108 *
109 * Return: 0 on success; -errno on failure.
110 */
fscrypt_zeroout_range(const struct inode * inode,pgoff_t lblk,sector_t pblk,unsigned int len)111 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
112 sector_t pblk, unsigned int len)
113 {
114 const struct fscrypt_inode_info *ci = inode->i_crypt_info;
115 const unsigned int du_bits = ci->ci_data_unit_bits;
116 const unsigned int du_size = 1U << du_bits;
117 const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits;
118 const unsigned int du_per_page = 1U << du_per_page_bits;
119 u64 du_index = (u64)lblk << (inode->i_blkbits - du_bits);
120 u64 du_remaining = (u64)len << (inode->i_blkbits - du_bits);
121 sector_t sector = pblk << (inode->i_blkbits - SECTOR_SHIFT);
122 struct page *pages[16]; /* write up to 16 pages at a time */
123 unsigned int nr_pages;
124 unsigned int i;
125 unsigned int offset;
126 struct bio *bio;
127 int ret, err;
128
129 if (len == 0)
130 return 0;
131
132 if (fscrypt_inode_uses_inline_crypto(inode))
133 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,
134 len);
135
136 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);
137 nr_pages = min_t(u64, ARRAY_SIZE(pages),
138 (du_remaining + du_per_page - 1) >> du_per_page_bits);
139
140 /*
141 * We need at least one page for ciphertext. Allocate the first one
142 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
143 *
144 * Any additional page allocations are allowed to fail, as they only
145 * help performance, and waiting on the mempool for them could deadlock.
146 */
147 for (i = 0; i < nr_pages; i++) {
148 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
149 GFP_NOWAIT | __GFP_NOWARN);
150 if (!pages[i])
151 break;
152 }
153 nr_pages = i;
154 if (WARN_ON_ONCE(nr_pages <= 0))
155 return -EINVAL;
156
157 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
158 bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS);
159
160 do {
161 bio->bi_iter.bi_sector = sector;
162
163 i = 0;
164 offset = 0;
165 do {
166 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, du_index,
167 ZERO_PAGE(0), pages[i],
168 du_size, offset,
169 GFP_NOFS);
170 if (err)
171 goto out;
172 du_index++;
173 sector += 1U << (du_bits - SECTOR_SHIFT);
174 du_remaining--;
175 offset += du_size;
176 if (offset == PAGE_SIZE || du_remaining == 0) {
177 ret = bio_add_page(bio, pages[i++], offset, 0);
178 if (WARN_ON_ONCE(ret != offset)) {
179 err = -EIO;
180 goto out;
181 }
182 offset = 0;
183 }
184 } while (i != nr_pages && du_remaining != 0);
185
186 err = submit_bio_wait(bio);
187 if (err)
188 goto out;
189 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE);
190 } while (du_remaining != 0);
191 err = 0;
192 out:
193 bio_put(bio);
194 for (i = 0; i < nr_pages; i++)
195 fscrypt_free_bounce_page(pages[i]);
196 return err;
197 }
198 EXPORT_SYMBOL(fscrypt_zeroout_range);
199