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