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/bio.h>
11#include <linux/export.h>
12#include <linux/module.h>
13#include <linux/namei.h>
14#include <linux/pagemap.h>
15
16#include "fscrypt_private.h"
17
18/**
19 * fscrypt_decrypt_bio() - decrypt the contents of a bio
20 * @bio: the bio to decrypt
21 *
22 * Decrypt the contents of a "read" bio following successful completion of the
23 * underlying disk read. The bio must be reading a whole number of blocks of an
24 * encrypted file directly into the page cache. If the bio is reading the
25 * ciphertext into bounce pages instead of the page cache (for example, because
26 * the file is also compressed, so decompression is required after decryption),
27 * then this function isn't applicable. This function may sleep, so it must be
28 * called from a workqueue rather than from the bio's bi_end_io callback.
29 *
30 * Return: %true on success; %false on failure. On failure, bio->bi_status is
31 * also set to an error status.
32 */
33bool fscrypt_decrypt_bio(struct bio *bio)
34{
35 struct folio_iter fi;
36
37 bio_for_each_folio_all(fi, bio) {
38 int err = fscrypt_decrypt_pagecache_blocks(folio: fi.folio, len: fi.length,
39 offs: fi.offset);
40
41 if (err) {
42 bio->bi_status = errno_to_blk_status(errno: err);
43 return false;
44 }
45 }
46 return true;
47}
48EXPORT_SYMBOL(fscrypt_decrypt_bio);
49
50static 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(bdev: inode->i_sb->s_bdev, BIO_MAX_VECS, opf: REQ_OP_WRITE,
62 GFP_NOFS);
63
64 while (len) {
65 unsigned int blocks_this_page = min(len, blocks_per_page);
66 unsigned int bytes_this_page = blocks_this_page << blockbits;
67
68 if (num_pages == 0) {
69 fscrypt_set_bio_crypt_ctx(bio, inode, first_lblk: lblk, GFP_NOFS);
70 bio->bi_iter.bi_sector =
71 pblk << (blockbits - SECTOR_SHIFT);
72 }
73 ret = bio_add_page(bio, ZERO_PAGE(0), len: bytes_this_page, off: 0);
74 if (WARN_ON_ONCE(ret != bytes_this_page)) {
75 err = -EIO;
76 goto out;
77 }
78 num_pages++;
79 len -= blocks_this_page;
80 lblk += blocks_this_page;
81 pblk += blocks_this_page;
82 if (num_pages == BIO_MAX_VECS || !len ||
83 !fscrypt_mergeable_bio(bio, inode, next_lblk: lblk)) {
84 err = submit_bio_wait(bio);
85 if (err)
86 goto out;
87 bio_reset(bio, bdev: inode->i_sb->s_bdev, opf: REQ_OP_WRITE);
88 num_pages = 0;
89 }
90 }
91out:
92 bio_put(bio);
93 return err;
94}
95
96/**
97 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
98 * @inode: the file's inode
99 * @lblk: the first file logical block to zero out
100 * @pblk: the first filesystem physical block to zero out
101 * @len: number of blocks to zero out
102 *
103 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
104 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
105 * both logically and physically contiguous. It's also assumed that the
106 * filesystem only uses a single block device, ->s_bdev.
107 *
108 * Note that since each block uses a different IV, this involves writing a
109 * different ciphertext to each block; we can't simply reuse the same one.
110 *
111 * Return: 0 on success; -errno on failure.
112 */
113int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
114 sector_t pblk, unsigned int len)
115{
116 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode);
117 const unsigned int du_bits = ci->ci_data_unit_bits;
118 const unsigned int du_size = 1U << du_bits;
119 const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits;
120 const unsigned int du_per_page = 1U << du_per_page_bits;
121 u64 du_index = (u64)lblk << (inode->i_blkbits - du_bits);
122 u64 du_remaining = (u64)len << (inode->i_blkbits - du_bits);
123 sector_t sector = pblk << (inode->i_blkbits - SECTOR_SHIFT);
124 struct page *pages[16]; /* write up to 16 pages at a time */
125 unsigned int nr_pages;
126 unsigned int i;
127 unsigned int offset;
128 struct bio *bio;
129 int ret, err;
130
131 if (len == 0)
132 return 0;
133
134 if (fscrypt_inode_uses_inline_crypto(inode))
135 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,
136 len);
137
138 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);
139 nr_pages = min_t(u64, ARRAY_SIZE(pages),
140 (du_remaining + du_per_page - 1) >> du_per_page_bits);
141
142 /*
143 * We need at least one page for ciphertext. Allocate the first one
144 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
145 *
146 * Any additional page allocations are allowed to fail, as they only
147 * help performance, and waiting on the mempool for them could deadlock.
148 */
149 for (i = 0; i < nr_pages; i++) {
150 pages[i] = fscrypt_alloc_bounce_page(gfp_flags: i == 0 ? GFP_NOFS :
151 GFP_NOWAIT);
152 if (!pages[i])
153 break;
154 }
155 nr_pages = i;
156 if (WARN_ON_ONCE(nr_pages <= 0))
157 return -EINVAL;
158
159 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
160 bio = bio_alloc(bdev: inode->i_sb->s_bdev, nr_vecs: nr_pages, opf: REQ_OP_WRITE, GFP_NOFS);
161
162 do {
163 bio->bi_iter.bi_sector = sector;
164
165 i = 0;
166 offset = 0;
167 do {
168 err = fscrypt_crypt_data_unit(ci, rw: FS_ENCRYPT, index: du_index,
169 ZERO_PAGE(0), dest_page: pages[i],
170 len: du_size, offs: offset);
171 if (err)
172 goto out;
173 du_index++;
174 sector += 1U << (du_bits - SECTOR_SHIFT);
175 du_remaining--;
176 offset += du_size;
177 if (offset == PAGE_SIZE || du_remaining == 0) {
178 ret = bio_add_page(bio, page: pages[i++], len: offset, off: 0);
179 if (WARN_ON_ONCE(ret != offset)) {
180 err = -EIO;
181 goto out;
182 }
183 offset = 0;
184 }
185 } while (i != nr_pages && du_remaining != 0);
186
187 err = submit_bio_wait(bio);
188 if (err)
189 goto out;
190 bio_reset(bio, bdev: inode->i_sb->s_bdev, opf: REQ_OP_WRITE);
191 } while (du_remaining != 0);
192 err = 0;
193out:
194 bio_put(bio);
195 for (i = 0; i < nr_pages; i++)
196 fscrypt_free_bounce_page(bounce_page: pages[i]);
197 return err;
198}
199EXPORT_SYMBOL(fscrypt_zeroout_range);
200

source code of linux/fs/crypto/bio.c