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 */ 33 bool 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(fi.folio, fi.length, 39 fi.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_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, 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 struct fscrypt_inode_info *ci = inode->i_crypt_info; 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(i == 0 ? GFP_NOFS : 151 GFP_NOWAIT | __GFP_NOWARN); 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(inode->i_sb->s_bdev, nr_pages, 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, FS_ENCRYPT, du_index, 169 ZERO_PAGE(0), pages[i], 170 du_size, 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, pages[i++], offset, 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, inode->i_sb->s_bdev, REQ_OP_WRITE); 191 } while (du_remaining != 0); 192 err = 0; 193 out: 194 bio_put(bio); 195 for (i = 0; i < nr_pages; i++) 196 fscrypt_free_bounce_page(pages[i]); 197 return err; 198 } 199 EXPORT_SYMBOL(fscrypt_zeroout_range); 200