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 struct fscrypt_zero_done { 51 atomic_t pending; 52 blk_status_t status; 53 struct completion done; 54 }; 55 56 static void fscrypt_zeroout_range_done(struct fscrypt_zero_done *done) 57 { 58 if (atomic_dec_and_test(&done->pending)) 59 complete(&done->done); 60 } 61 62 static void fscrypt_zeroout_range_end_io(struct bio *bio) 63 { 64 struct fscrypt_zero_done *done = bio->bi_private; 65 66 if (bio->bi_status) 67 cmpxchg(&done->status, 0, bio->bi_status); 68 fscrypt_zeroout_range_done(done); 69 bio_put(bio); 70 } 71 72 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode, 73 loff_t pos, sector_t sector, 74 u64 len) 75 { 76 struct fscrypt_zero_done done = { 77 .pending = ATOMIC_INIT(1), 78 .done = COMPLETION_INITIALIZER_ONSTACK(done.done), 79 }; 80 81 while (len) { 82 struct bio *bio; 83 unsigned int n; 84 85 bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE, 86 GFP_NOFS); 87 bio->bi_iter.bi_sector = sector; 88 bio->bi_private = &done; 89 bio->bi_end_io = fscrypt_zeroout_range_end_io; 90 fscrypt_set_bio_crypt_ctx(bio, inode, pos, GFP_NOFS); 91 92 for (n = 0; n < BIO_MAX_VECS; n++) { 93 unsigned int bytes_this_page = min(len, PAGE_SIZE); 94 95 __bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); 96 len -= bytes_this_page; 97 pos += bytes_this_page; 98 sector += (bytes_this_page >> SECTOR_SHIFT); 99 if (!len || !fscrypt_mergeable_bio(bio, inode, pos)) 100 break; 101 } 102 103 atomic_inc(&done.pending); 104 blk_crypto_submit_bio(bio); 105 } 106 107 fscrypt_zeroout_range_done(&done); 108 109 wait_for_completion(&done.done); 110 return blk_status_to_errno(done.status); 111 } 112 113 /** 114 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file 115 * @inode: the file's inode 116 * @pos: the first file position (in bytes) to zero out 117 * @sector: the first sector to zero out 118 * @len: bytes to zero out 119 * 120 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write 121 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be 122 * both logically and physically contiguous. It's also assumed that the 123 * filesystem only uses a single block device, ->s_bdev. @len must be a 124 * multiple of the file system logical block size. 125 * 126 * Note that since each block uses a different IV, this involves writing a 127 * different ciphertext to each block; we can't simply reuse the same one. 128 * 129 * Return: 0 on success; -errno on failure. 130 */ 131 int fscrypt_zeroout_range(const struct inode *inode, loff_t pos, 132 sector_t sector, u64 len) 133 { 134 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode); 135 const unsigned int du_bits = ci->ci_data_unit_bits; 136 const unsigned int du_size = 1U << du_bits; 137 const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits; 138 const unsigned int du_per_page = 1U << du_per_page_bits; 139 u64 du_index = pos >> du_bits; 140 u64 du_remaining = len >> du_bits; 141 struct page *pages[16]; /* write up to 16 pages at a time */ 142 unsigned int nr_pages; 143 unsigned int i; 144 unsigned int offset; 145 struct bio *bio; 146 int ret, err; 147 148 if (len == 0) 149 return 0; 150 151 if (fscrypt_inode_uses_inline_crypto(inode)) 152 return fscrypt_zeroout_range_inline_crypt(inode, pos, sector, 153 len); 154 155 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); 156 nr_pages = min_t(u64, ARRAY_SIZE(pages), 157 (du_remaining + du_per_page - 1) >> du_per_page_bits); 158 159 /* 160 * We need at least one page for ciphertext. Allocate the first one 161 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail. 162 * 163 * Any additional page allocations are allowed to fail, as they only 164 * help performance, and waiting on the mempool for them could deadlock. 165 */ 166 for (i = 0; i < nr_pages; i++) { 167 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS : 168 GFP_NOWAIT); 169 if (!pages[i]) 170 break; 171 } 172 nr_pages = i; 173 if (WARN_ON_ONCE(nr_pages <= 0)) 174 return -EINVAL; 175 176 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ 177 bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS); 178 179 do { 180 bio->bi_iter.bi_sector = sector; 181 182 i = 0; 183 offset = 0; 184 do { 185 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, du_index, 186 ZERO_PAGE(0), pages[i], 187 du_size, offset); 188 if (err) 189 goto out; 190 du_index++; 191 sector += 1U << (du_bits - SECTOR_SHIFT); 192 du_remaining--; 193 offset += du_size; 194 if (offset == PAGE_SIZE || du_remaining == 0) { 195 ret = bio_add_page(bio, pages[i++], offset, 0); 196 if (WARN_ON_ONCE(ret != offset)) { 197 err = -EIO; 198 goto out; 199 } 200 offset = 0; 201 } 202 } while (i != nr_pages && du_remaining != 0); 203 204 err = submit_bio_wait(bio); 205 if (err) 206 goto out; 207 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); 208 } while (du_remaining != 0); 209 err = 0; 210 out: 211 bio_put(bio); 212 for (i = 0; i < nr_pages; i++) 213 fscrypt_free_bounce_page(pages[i]); 214 return err; 215 } 216 EXPORT_SYMBOL(fscrypt_zeroout_range); 217