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 * Return: %true on success; %false on failure. On failure, bio->bi_status is 29 * also set to an error status. 30 */ 31bool fscrypt_decrypt_bio(struct bio *bio) 32{ 33 struct folio_iter fi; 34 35 bio_for_each_folio_all(fi, bio) { 36 int err = fscrypt_decrypt_pagecache_blocks(fi.folio, fi.length, 37 fi.offset); 38 39 if (err) { 40 bio->bi_status = errno_to_blk_status(err); 41 return false; 42 } 43 } 44 return true; 45} 46EXPORT_SYMBOL(fscrypt_decrypt_bio); 47 48static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode, 49 pgoff_t lblk, sector_t pblk, 50 unsigned int len) 51{ 52 const unsigned int blockbits = inode->i_blkbits; 53 const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits); 54 struct bio *bio; 55 int ret, err = 0; 56 int num_pages = 0; 57 58 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ 59 bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE, 60 GFP_NOFS); 61 62 while (len) { 63 unsigned int blocks_this_page = min(len, blocks_per_page); 64 unsigned int bytes_this_page = blocks_this_page << blockbits; 65 66 if (num_pages == 0) { 67 fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS); 68 bio->bi_iter.bi_sector = 69 pblk << (blockbits - SECTOR_SHIFT); 70 } 71 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); 72 if (WARN_ON_ONCE(ret != bytes_this_page)) { 73 err = -EIO; 74 goto out; 75 } 76 num_pages++; 77 len -= blocks_this_page; 78 lblk += blocks_this_page; 79 pblk += blocks_this_page; 80 if (num_pages == BIO_MAX_VECS || !len || 81 !fscrypt_mergeable_bio(bio, inode, lblk)) { 82 err = submit_bio_wait(bio); 83 if (err) 84 goto out; 85 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); 86 num_pages = 0; 87 } 88 } 89out: 90 bio_put(bio); 91 return err; 92} 93 94/** 95 * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file 96 * @inode: the file's inode 97 * @lblk: the first file logical block to zero out 98 * @pblk: the first filesystem physical block to zero out 99 * @len: number of blocks to zero out 100 * 101 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write 102 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be 103 * both logically and physically contiguous. It's also assumed that the 104 * filesystem only uses a single block device, ->s_bdev. 105 * 106 * Note that since each block uses a different IV, this involves writing a 107 * different ciphertext to each block; we can't simply reuse the same one. 108 * 109 * Return: 0 on success; -errno on failure. 110 */ 111int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, 112 sector_t pblk, unsigned int len) 113{ 114 const unsigned int blockbits = inode->i_blkbits; 115 const unsigned int blocksize = 1 << blockbits; 116 const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits; 117 const unsigned int blocks_per_page = 1 << blocks_per_page_bits; 118 struct page *pages[16]; /* write up to 16 pages at a time */ 119 unsigned int nr_pages; 120 unsigned int i; 121 unsigned int offset; 122 struct bio *bio; 123 int ret, err; 124 125 if (len == 0) 126 return 0; 127 128 if (fscrypt_inode_uses_inline_crypto(inode)) 129 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk, 130 len); 131 132 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); 133 nr_pages = min_t(unsigned int, ARRAY_SIZE(pages), 134 (len + blocks_per_page - 1) >> blocks_per_page_bits); 135 136 /* 137 * We need at least one page for ciphertext. Allocate the first one 138 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail. 139 * 140 * Any additional page allocations are allowed to fail, as they only 141 * help performance, and waiting on the mempool for them could deadlock. 142 */ 143 for (i = 0; i < nr_pages; i++) { 144 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS : 145 GFP_NOWAIT | __GFP_NOWARN); 146 if (!pages[i]) 147 break; 148 } 149 nr_pages = i; 150 if (WARN_ON_ONCE(nr_pages <= 0)) 151 return -EINVAL; 152 153 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ 154 bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS); 155 156 do { 157 bio->bi_iter.bi_sector = pblk << (blockbits - 9); 158 159 i = 0; 160 offset = 0; 161 do { 162 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk, 163 ZERO_PAGE(0), pages[i], 164 blocksize, offset, GFP_NOFS); 165 if (err) 166 goto out; 167 lblk++; 168 pblk++; 169 len--; 170 offset += blocksize; 171 if (offset == PAGE_SIZE || len == 0) { 172 ret = bio_add_page(bio, pages[i++], offset, 0); 173 if (WARN_ON_ONCE(ret != offset)) { 174 err = -EIO; 175 goto out; 176 } 177 offset = 0; 178 } 179 } while (i != nr_pages && len != 0); 180 181 err = submit_bio_wait(bio); 182 if (err) 183 goto out; 184 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); 185 } while (len != 0); 186 err = 0; 187out: 188 bio_put(bio); 189 for (i = 0; i < nr_pages; i++) 190 fscrypt_free_bounce_page(pages[i]); 191 return err; 192} 193EXPORT_SYMBOL(fscrypt_zeroout_range); 194