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 pgoff_t lblk, sector_t sector, 74 unsigned int len) 75 { 76 const unsigned int blockbits = inode->i_blkbits; 77 const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits); 78 struct fscrypt_zero_done done = { 79 .pending = ATOMIC_INIT(1), 80 .done = COMPLETION_INITIALIZER_ONSTACK(done.done), 81 }; 82 83 while (len) { 84 struct bio *bio; 85 unsigned int n; 86 87 bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE, 88 GFP_NOFS); 89 bio->bi_iter.bi_sector = sector; 90 bio->bi_private = &done; 91 bio->bi_end_io = fscrypt_zeroout_range_end_io; 92 fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS); 93 94 for (n = 0; n < BIO_MAX_VECS; n++) { 95 unsigned int blocks_this_page = 96 min(len, blocks_per_page); 97 unsigned int bytes_this_page = blocks_this_page << blockbits; 98 99 __bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); 100 len -= blocks_this_page; 101 lblk += blocks_this_page; 102 sector += (bytes_this_page >> SECTOR_SHIFT); 103 if (!len || !fscrypt_mergeable_bio(bio, inode, lblk)) 104 break; 105 } 106 107 atomic_inc(&done.pending); 108 blk_crypto_submit_bio(bio); 109 } 110 111 fscrypt_zeroout_range_done(&done); 112 113 wait_for_completion(&done.done); 114 return blk_status_to_errno(done.status); 115 } 116 117 /** 118 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file 119 * @inode: the file's inode 120 * @lblk: the first file logical block to zero out 121 * @pblk: the first filesystem physical block to zero out 122 * @len: number of blocks to zero out 123 * 124 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write 125 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be 126 * both logically and physically contiguous. It's also assumed that the 127 * filesystem only uses a single block device, ->s_bdev. 128 * 129 * Note that since each block uses a different IV, this involves writing a 130 * different ciphertext to each block; we can't simply reuse the same one. 131 * 132 * Return: 0 on success; -errno on failure. 133 */ 134 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, 135 sector_t pblk, unsigned int len) 136 { 137 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode); 138 const unsigned int du_bits = ci->ci_data_unit_bits; 139 const unsigned int du_size = 1U << du_bits; 140 const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits; 141 const unsigned int du_per_page = 1U << du_per_page_bits; 142 u64 du_index = (u64)lblk << (inode->i_blkbits - du_bits); 143 u64 du_remaining = (u64)len << (inode->i_blkbits - du_bits); 144 sector_t sector = pblk << (inode->i_blkbits - SECTOR_SHIFT); 145 struct page *pages[16]; /* write up to 16 pages at a time */ 146 unsigned int nr_pages; 147 unsigned int i; 148 unsigned int offset; 149 struct bio *bio; 150 int ret, err; 151 152 if (len == 0) 153 return 0; 154 155 if (fscrypt_inode_uses_inline_crypto(inode)) 156 return fscrypt_zeroout_range_inline_crypt(inode, lblk, sector, 157 len); 158 159 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); 160 nr_pages = min_t(u64, ARRAY_SIZE(pages), 161 (du_remaining + du_per_page - 1) >> du_per_page_bits); 162 163 /* 164 * We need at least one page for ciphertext. Allocate the first one 165 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail. 166 * 167 * Any additional page allocations are allowed to fail, as they only 168 * help performance, and waiting on the mempool for them could deadlock. 169 */ 170 for (i = 0; i < nr_pages; i++) { 171 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS : 172 GFP_NOWAIT); 173 if (!pages[i]) 174 break; 175 } 176 nr_pages = i; 177 if (WARN_ON_ONCE(nr_pages <= 0)) 178 return -EINVAL; 179 180 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ 181 bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS); 182 183 do { 184 bio->bi_iter.bi_sector = sector; 185 186 i = 0; 187 offset = 0; 188 do { 189 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, du_index, 190 ZERO_PAGE(0), pages[i], 191 du_size, offset); 192 if (err) 193 goto out; 194 du_index++; 195 sector += 1U << (du_bits - SECTOR_SHIFT); 196 du_remaining--; 197 offset += du_size; 198 if (offset == PAGE_SIZE || du_remaining == 0) { 199 ret = bio_add_page(bio, pages[i++], offset, 0); 200 if (WARN_ON_ONCE(ret != offset)) { 201 err = -EIO; 202 goto out; 203 } 204 offset = 0; 205 } 206 } while (i != nr_pages && du_remaining != 0); 207 208 err = submit_bio_wait(bio); 209 if (err) 210 goto out; 211 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); 212 } while (du_remaining != 0); 213 err = 0; 214 out: 215 bio_put(bio); 216 for (i = 0; i < nr_pages; i++) 217 fscrypt_free_bounce_page(pages[i]); 218 return err; 219 } 220 EXPORT_SYMBOL(fscrypt_zeroout_range); 221