142 lines
3.9 KiB
C
142 lines
3.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This contains encryption functions for per-file encryption.
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*
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* Copyright (C) 2015, Google, Inc.
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* Copyright (C) 2015, Motorola Mobility
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*
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* Written by Michael Halcrow, 2014.
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*
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* Filename encryption additions
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* Uday Savagaonkar, 2014
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* Encryption policy handling additions
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* Ildar Muslukhov, 2014
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* Add fscrypt_pullback_bio_page()
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* Jaegeuk Kim, 2015.
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*
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* This has not yet undergone a rigorous security audit.
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*
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* The usage of AES-XTS should conform to recommendations in NIST
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* Special Publication 800-38E and IEEE P1619/D16.
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*/
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#include <linux/pagemap.h>
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#include <linux/module.h>
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#include <linux/bio.h>
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#include <linux/namei.h>
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#include "fscrypt_private.h"
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void fscrypt_decrypt_bio(struct bio *bio)
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{
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struct bio_vec *bv;
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struct bvec_iter_all iter_all;
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bio_for_each_segment_all(bv, bio, iter_all) {
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struct page *page = bv->bv_page;
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int ret = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len,
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bv->bv_offset);
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if (ret)
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SetPageError(page);
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}
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}
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EXPORT_SYMBOL(fscrypt_decrypt_bio);
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/**
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* fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
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* @inode: the file's inode
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* @lblk: the first file logical block to zero out
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* @pblk: the first filesystem physical block to zero out
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* @len: number of blocks to zero out
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*
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* Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
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* ciphertext blocks which decrypt to the all-zeroes block. The blocks must be
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* both logically and physically contiguous. It's also assumed that the
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* filesystem only uses a single block device, ->s_bdev.
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*
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* Note that since each block uses a different IV, this involves writing a
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* different ciphertext to each block; we can't simply reuse the same one.
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*
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* Return: 0 on success; -errno on failure.
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*/
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int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
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sector_t pblk, unsigned int len)
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{
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const unsigned int blockbits = inode->i_blkbits;
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const unsigned int blocksize = 1 << blockbits;
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const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
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const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
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struct page *pages[16]; /* write up to 16 pages at a time */
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unsigned int nr_pages;
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unsigned int i;
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unsigned int offset;
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struct bio *bio;
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int ret, err;
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if (len == 0)
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return 0;
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BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_PAGES);
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nr_pages = min_t(unsigned int, ARRAY_SIZE(pages),
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(len + blocks_per_page - 1) >> blocks_per_page_bits);
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/*
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* We need at least one page for ciphertext. Allocate the first one
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* from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
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*
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* Any additional page allocations are allowed to fail, as they only
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* help performance, and waiting on the mempool for them could deadlock.
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*/
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for (i = 0; i < nr_pages; i++) {
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pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
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GFP_NOWAIT | __GFP_NOWARN);
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if (!pages[i])
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break;
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}
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nr_pages = i;
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if (WARN_ON(nr_pages <= 0))
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return -EINVAL;
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/* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
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bio = bio_alloc(GFP_NOFS, nr_pages);
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do {
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bio_set_dev(bio, inode->i_sb->s_bdev);
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bio->bi_iter.bi_sector = pblk << (blockbits - 9);
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bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
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i = 0;
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offset = 0;
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do {
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err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
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ZERO_PAGE(0), pages[i],
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blocksize, offset, GFP_NOFS);
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if (err)
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goto out;
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lblk++;
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pblk++;
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len--;
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offset += blocksize;
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if (offset == PAGE_SIZE || len == 0) {
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ret = bio_add_page(bio, pages[i++], offset, 0);
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if (WARN_ON(ret != offset)) {
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err = -EIO;
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goto out;
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}
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offset = 0;
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}
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} while (i != nr_pages && len != 0);
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err = submit_bio_wait(bio);
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if (err)
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goto out;
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bio_reset(bio);
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} while (len != 0);
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err = 0;
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out:
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bio_put(bio);
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for (i = 0; i < nr_pages; i++)
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fscrypt_free_bounce_page(pages[i]);
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return err;
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}
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EXPORT_SYMBOL(fscrypt_zeroout_range);
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