1 // SPDX-License-Identifier: GPL-2.0
3 * This contains encryption functions for per-file encryption.
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility
8 * Written by Michael Halcrow, 2014.
10 * Filename encryption additions
11 * Uday Savagaonkar, 2014
12 * Encryption policy handling additions
13 * Ildar Muslukhov, 2014
14 * Add fscrypt_pullback_bio_page()
17 * This has not yet undergone a rigorous security audit.
19 * The usage of AES-XTS should conform to recommendations in NIST
20 * Special Publication 800-38E and IEEE P1619/D16.
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"
29 void fscrypt_decrypt_bio(struct bio *bio)
32 struct bvec_iter_all iter_all;
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,
42 EXPORT_SYMBOL(fscrypt_decrypt_bio);
45 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
46 * @inode: the file's inode
47 * @lblk: the first file logical block to zero out
48 * @pblk: the first filesystem physical block to zero out
49 * @len: number of blocks to zero out
51 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
52 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
53 * both logically and physically contiguous. It's also assumed that the
54 * filesystem only uses a single block device, ->s_bdev.
56 * Note that since each block uses a different IV, this involves writing a
57 * different ciphertext to each block; we can't simply reuse the same one.
59 * Return: 0 on success; -errno on failure.
61 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
62 sector_t pblk, unsigned int len)
64 const unsigned int blockbits = inode->i_blkbits;
65 const unsigned int blocksize = 1 << blockbits;
66 const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
67 const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
68 struct page *pages[16]; /* write up to 16 pages at a time */
69 unsigned int nr_pages;
78 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_PAGES);
79 nr_pages = min_t(unsigned int, ARRAY_SIZE(pages),
80 (len + blocks_per_page - 1) >> blocks_per_page_bits);
83 * We need at least one page for ciphertext. Allocate the first one
84 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
86 * Any additional page allocations are allowed to fail, as they only
87 * help performance, and waiting on the mempool for them could deadlock.
89 for (i = 0; i < nr_pages; i++) {
90 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
91 GFP_NOWAIT | __GFP_NOWARN);
96 if (WARN_ON(nr_pages <= 0))
99 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
100 bio = bio_alloc(GFP_NOFS, nr_pages);
103 bio_set_dev(bio, inode->i_sb->s_bdev);
104 bio->bi_iter.bi_sector = pblk << (blockbits - 9);
105 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
110 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
111 ZERO_PAGE(0), pages[i],
112 blocksize, offset, GFP_NOFS);
119 if (offset == PAGE_SIZE || len == 0) {
120 ret = bio_add_page(bio, pages[i++], offset, 0);
121 if (WARN_ON(ret != offset)) {
127 } while (i != nr_pages && len != 0);
129 err = submit_bio_wait(bio);
137 for (i = 0; i < nr_pages; i++)
138 fscrypt_free_bounce_page(pages[i]);
141 EXPORT_SYMBOL(fscrypt_zeroout_range);