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1// SPDX-License-Identifier: GPL-2.02/*3 * Utility functions for file contents encryption/decryption on4 * block device-based filesystems.5 *6 * Copyright (C) 2015, Google, Inc.7 * Copyright (C) 2015, Motorola Mobility8 */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 bio18 * @bio: the bio to decrypt19 *20 * Decrypt the contents of a "read" bio following successful completion of the21 * underlying disk read. The bio must be reading a whole number of blocks of an22 * encrypted file directly into the page cache. If the bio is reading the23 * ciphertext into bounce pages instead of the page cache (for example, because24 * 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 be26 * 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 is29 * 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 file96 * @inode: the file's inode97 * @lblk: the first file logical block to zero out98 * @pblk: the first filesystem physical block to zero out99 * @len: number of blocks to zero out100 *101 * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write102 * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be103 * both logically and physically contiguous. It's also assumed that the104 * filesystem only uses a single block device, ->s_bdev.105 *106 * Note that since each block uses a different IV, this involves writing a107 * 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 struct fscrypt_inode_info *ci = inode->i_crypt_info;115 const unsigned int du_bits = ci->ci_data_unit_bits;116 const unsigned int du_size = 1U << du_bits;117 const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits;118 const unsigned int du_per_page = 1U << du_per_page_bits;119 u64 du_index = (u64)lblk << (inode->i_blkbits - du_bits);120 u64 du_remaining = (u64)len << (inode->i_blkbits - du_bits);121 sector_t sector = pblk << (inode->i_blkbits - SECTOR_SHIFT);122 struct page *pages[16]; /* write up to 16 pages at a time */123 unsigned int nr_pages;124 unsigned int i;125 unsigned int offset;126 struct bio *bio;127 int ret, err;128 129 if (len == 0)130 return 0;131 132 if (fscrypt_inode_uses_inline_crypto(inode))133 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,134 len);135 136 BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);137 nr_pages = min_t(u64, ARRAY_SIZE(pages),138 (du_remaining + du_per_page - 1) >> du_per_page_bits);139 140 /*141 * We need at least one page for ciphertext. Allocate the first one142 * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.143 *144 * Any additional page allocations are allowed to fail, as they only145 * help performance, and waiting on the mempool for them could deadlock.146 */147 for (i = 0; i < nr_pages; i++) {148 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :149 GFP_NOWAIT | __GFP_NOWARN);150 if (!pages[i])151 break;152 }153 nr_pages = i;154 if (WARN_ON_ONCE(nr_pages <= 0))155 return -EINVAL;156 157 /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */158 bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS);159 160 do {161 bio->bi_iter.bi_sector = sector;162 163 i = 0;164 offset = 0;165 do {166 err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, du_index,167 ZERO_PAGE(0), pages[i],168 du_size, offset,169 GFP_NOFS);170 if (err)171 goto out;172 du_index++;173 sector += 1U << (du_bits - SECTOR_SHIFT);174 du_remaining--;175 offset += du_size;176 if (offset == PAGE_SIZE || du_remaining == 0) {177 ret = bio_add_page(bio, pages[i++], offset, 0);178 if (WARN_ON_ONCE(ret != offset)) {179 err = -EIO;180 goto out;181 }182 offset = 0;183 }184 } while (i != nr_pages && du_remaining != 0);185 186 err = submit_bio_wait(bio);187 if (err)188 goto out;189 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE);190 } while (du_remaining != 0);191 err = 0;192out:193 bio_put(bio);194 for (i = 0; i < nr_pages; i++)195 fscrypt_free_bounce_page(pages[i]);196 return err;197}198EXPORT_SYMBOL(fscrypt_zeroout_range);199