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 * This function sets PG_error on any pages that contain any blocks that failed 29 * to be decrypted. The filesystem must not mark such pages uptodate. 30 */ 31 void 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 ret = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len, 39 bv->bv_offset); 40 if (ret) 41 SetPageError(page); 42 } 43 } 44 EXPORT_SYMBOL(fscrypt_decrypt_bio); 45 46 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode, 47 pgoff_t lblk, sector_t pblk, 48 unsigned int len) 49 { 50 const unsigned int blockbits = inode->i_blkbits; 51 const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits); 52 struct bio *bio; 53 int ret, err = 0; 54 int num_pages = 0; 55 56 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ 57 bio = bio_alloc(GFP_NOFS, BIO_MAX_VECS); 58 59 while (len) { 60 unsigned int blocks_this_page = min(len, blocks_per_page); 61 unsigned int bytes_this_page = blocks_this_page << blockbits; 62 63 if (num_pages == 0) { 64 fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS); 65 bio_set_dev(bio, inode->i_sb->s_bdev); 66 bio->bi_iter.bi_sector = 67 pblk << (blockbits - SECTOR_SHIFT); 68 bio_set_op_attrs(bio, REQ_OP_WRITE, 0); 69 } 70 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); 71 if (WARN_ON(ret != bytes_this_page)) { 72 err = -EIO; 73 goto out; 74 } 75 num_pages++; 76 len -= blocks_this_page; 77 lblk += blocks_this_page; 78 pblk += blocks_this_page; 79 if (num_pages == BIO_MAX_VECS || !len || 80 !fscrypt_mergeable_bio(bio, inode, lblk)) { 81 err = submit_bio_wait(bio); 82 if (err) 83 goto out; 84 bio_reset(bio); 85 num_pages = 0; 86 } 87 } 88 out: 89 bio_put(bio); 90 return err; 91 } 92 93 /** 94 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file 95 * @inode: the file's inode 96 * @lblk: the first file logical block to zero out 97 * @pblk: the first filesystem physical block to zero out 98 * @len: number of blocks to zero out 99 * 100 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write 101 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be 102 * both logically and physically contiguous. It's also assumed that the 103 * filesystem only uses a single block device, ->s_bdev. 104 * 105 * Note that since each block uses a different IV, this involves writing a 106 * different ciphertext to each block; we can't simply reuse the same one. 107 * 108 * Return: 0 on success; -errno on failure. 109 */ 110 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, 111 sector_t pblk, unsigned int len) 112 { 113 const unsigned int blockbits = inode->i_blkbits; 114 const unsigned int blocksize = 1 << blockbits; 115 const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits; 116 const unsigned int blocks_per_page = 1 << blocks_per_page_bits; 117 struct page *pages[16]; /* write up to 16 pages at a time */ 118 unsigned int nr_pages; 119 unsigned int i; 120 unsigned int offset; 121 struct bio *bio; 122 int ret, err; 123 124 if (len == 0) 125 return 0; 126 127 if (fscrypt_inode_uses_inline_crypto(inode)) 128 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk, 129 len); 130 131 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); 132 nr_pages = min_t(unsigned int, ARRAY_SIZE(pages), 133 (len + blocks_per_page - 1) >> blocks_per_page_bits); 134 135 /* 136 * We need at least one page for ciphertext. Allocate the first one 137 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail. 138 * 139 * Any additional page allocations are allowed to fail, as they only 140 * help performance, and waiting on the mempool for them could deadlock. 141 */ 142 for (i = 0; i < nr_pages; i++) { 143 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS : 144 GFP_NOWAIT | __GFP_NOWARN); 145 if (!pages[i]) 146 break; 147 } 148 nr_pages = i; 149 if (WARN_ON(nr_pages <= 0)) 150 return -EINVAL; 151 152 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ 153 bio = bio_alloc(GFP_NOFS, nr_pages); 154 155 do { 156 bio_set_dev(bio, inode->i_sb->s_bdev); 157 bio->bi_iter.bi_sector = pblk << (blockbits - 9); 158 bio_set_op_attrs(bio, REQ_OP_WRITE, 0); 159 160 i = 0; 161 offset = 0; 162 do { 163 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk, 164 ZERO_PAGE(0), pages[i], 165 blocksize, offset, GFP_NOFS); 166 if (err) 167 goto out; 168 lblk++; 169 pblk++; 170 len--; 171 offset += blocksize; 172 if (offset == PAGE_SIZE || len == 0) { 173 ret = bio_add_page(bio, pages[i++], offset, 0); 174 if (WARN_ON(ret != offset)) { 175 err = -EIO; 176 goto out; 177 } 178 offset = 0; 179 } 180 } while (i != nr_pages && len != 0); 181 182 err = submit_bio_wait(bio); 183 if (err) 184 goto out; 185 bio_reset(bio); 186 } while (len != 0); 187 err = 0; 188 out: 189 bio_put(bio); 190 for (i = 0; i < nr_pages; i++) 191 fscrypt_free_bounce_page(pages[i]); 192 return err; 193 } 194 EXPORT_SYMBOL(fscrypt_zeroout_range); 195