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 */ 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 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(inode->i_sb->s_bdev, BIO_MAX_VECS, 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, lblk, GFP_NOFS); 70 bio->bi_iter.bi_sector = 71 pblk << (blockbits - SECTOR_SHIFT); 72 } 73 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); 74 if (WARN_ON(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, lblk)) { 84 err = submit_bio_wait(bio); 85 if (err) 86 goto out; 87 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); 88 num_pages = 0; 89 } 90 } 91 out: 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 */ 113 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, 114 sector_t pblk, unsigned int len) 115 { 116 const unsigned int blockbits = inode->i_blkbits; 117 const unsigned int blocksize = 1 << blockbits; 118 const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits; 119 const unsigned int blocks_per_page = 1 << blocks_per_page_bits; 120 struct page *pages[16]; /* write up to 16 pages at a time */ 121 unsigned int nr_pages; 122 unsigned int i; 123 unsigned int offset; 124 struct bio *bio; 125 int ret, err; 126 127 if (len == 0) 128 return 0; 129 130 if (fscrypt_inode_uses_inline_crypto(inode)) 131 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk, 132 len); 133 134 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); 135 nr_pages = min_t(unsigned int, ARRAY_SIZE(pages), 136 (len + blocks_per_page - 1) >> blocks_per_page_bits); 137 138 /* 139 * We need at least one page for ciphertext. Allocate the first one 140 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail. 141 * 142 * Any additional page allocations are allowed to fail, as they only 143 * help performance, and waiting on the mempool for them could deadlock. 144 */ 145 for (i = 0; i < nr_pages; i++) { 146 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS : 147 GFP_NOWAIT | __GFP_NOWARN); 148 if (!pages[i]) 149 break; 150 } 151 nr_pages = i; 152 if (WARN_ON(nr_pages <= 0)) 153 return -EINVAL; 154 155 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ 156 bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS); 157 158 do { 159 bio->bi_iter.bi_sector = pblk << (blockbits - 9); 160 161 i = 0; 162 offset = 0; 163 do { 164 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk, 165 ZERO_PAGE(0), pages[i], 166 blocksize, offset, GFP_NOFS); 167 if (err) 168 goto out; 169 lblk++; 170 pblk++; 171 len--; 172 offset += blocksize; 173 if (offset == PAGE_SIZE || len == 0) { 174 ret = bio_add_page(bio, pages[i++], offset, 0); 175 if (WARN_ON(ret != offset)) { 176 err = -EIO; 177 goto out; 178 } 179 offset = 0; 180 } 181 } while (i != nr_pages && len != 0); 182 183 err = submit_bio_wait(bio); 184 if (err) 185 goto out; 186 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); 187 } while (len != 0); 188 err = 0; 189 out: 190 bio_put(bio); 191 for (i = 0; i < nr_pages; i++) 192 fscrypt_free_bounce_page(pages[i]); 193 return err; 194 } 195 EXPORT_SYMBOL(fscrypt_zeroout_range); 196