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Diffstat (limited to '')
| -rw-r--r-- | fs/crypto/bio.c | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c new file mode 100644 index 000000000..1b4403136 --- /dev/null +++ b/fs/crypto/bio.c @@ -0,0 +1,195 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Utility functions for file contents encryption/decryption on + * block device-based filesystems. + * + * Copyright (C) 2015, Google, Inc. + * Copyright (C) 2015, Motorola Mobility + */ + +#include <linux/pagemap.h> +#include <linux/module.h> +#include <linux/bio.h> +#include <linux/namei.h> +#include "fscrypt_private.h" + +/** + * fscrypt_decrypt_bio() - decrypt the contents of a bio + * @bio: the bio to decrypt + * + * Decrypt the contents of a "read" bio following successful completion of the + * underlying disk read. The bio must be reading a whole number of blocks of an + * encrypted file directly into the page cache. If the bio is reading the + * ciphertext into bounce pages instead of the page cache (for example, because + * the file is also compressed, so decompression is required after decryption), + * then this function isn't applicable. This function may sleep, so it must be + * called from a workqueue rather than from the bio's bi_end_io callback. + * + * Return: %true on success; %false on failure. On failure, bio->bi_status is + * also set to an error status. + */ +bool fscrypt_decrypt_bio(struct bio *bio) +{ + struct bio_vec *bv; + struct bvec_iter_all iter_all; + + bio_for_each_segment_all(bv, bio, iter_all) { + struct page *page = bv->bv_page; + int err = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len, + bv->bv_offset); + + if (err) { + bio->bi_status = errno_to_blk_status(err); + return false; + } + } + return true; +} +EXPORT_SYMBOL(fscrypt_decrypt_bio); + +static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode, + pgoff_t lblk, sector_t pblk, + unsigned int len) +{ + const unsigned int blockbits = inode->i_blkbits; + const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits); + struct bio *bio; + int ret, err = 0; + int num_pages = 0; + + /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ + bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE, + GFP_NOFS); + + while (len) { + unsigned int blocks_this_page = min(len, blocks_per_page); + unsigned int bytes_this_page = blocks_this_page << blockbits; + + if (num_pages == 0) { + fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS); + bio->bi_iter.bi_sector = + pblk << (blockbits - SECTOR_SHIFT); + } + ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); + if (WARN_ON(ret != bytes_this_page)) { + err = -EIO; + goto out; + } + num_pages++; + len -= blocks_this_page; + lblk += blocks_this_page; + pblk += blocks_this_page; + if (num_pages == BIO_MAX_VECS || !len || + !fscrypt_mergeable_bio(bio, inode, lblk)) { + err = submit_bio_wait(bio); + if (err) + goto out; + bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); + num_pages = 0; + } + } +out: + bio_put(bio); + return err; +} + +/** + * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file + * @inode: the file's inode + * @lblk: the first file logical block to zero out + * @pblk: the first filesystem physical block to zero out + * @len: number of blocks to zero out + * + * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write + * ciphertext blocks which decrypt to the all-zeroes block. The blocks must be + * both logically and physically contiguous. It's also assumed that the + * filesystem only uses a single block device, ->s_bdev. + * + * Note that since each block uses a different IV, this involves writing a + * different ciphertext to each block; we can't simply reuse the same one. + * + * Return: 0 on success; -errno on failure. + */ +int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk, + sector_t pblk, unsigned int len) +{ + const unsigned int blockbits = inode->i_blkbits; + const unsigned int blocksize = 1 << blockbits; + const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits; + const unsigned int blocks_per_page = 1 << blocks_per_page_bits; + struct page *pages[16]; /* write up to 16 pages at a time */ + unsigned int nr_pages; + unsigned int i; + unsigned int offset; + struct bio *bio; + int ret, err; + + if (len == 0) + return 0; + + if (fscrypt_inode_uses_inline_crypto(inode)) + return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk, + len); + + BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); + nr_pages = min_t(unsigned int, ARRAY_SIZE(pages), + (len + blocks_per_page - 1) >> blocks_per_page_bits); + + /* + * We need at least one page for ciphertext. Allocate the first one + * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail. + * + * Any additional page allocations are allowed to fail, as they only + * help performance, and waiting on the mempool for them could deadlock. + */ + for (i = 0; i < nr_pages; i++) { + pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS : + GFP_NOWAIT | __GFP_NOWARN); + if (!pages[i]) + break; + } + nr_pages = i; + if (WARN_ON(nr_pages <= 0)) + return -EINVAL; + + /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ + bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS); + + do { + bio->bi_iter.bi_sector = pblk << (blockbits - 9); + + i = 0; + offset = 0; + do { + err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk, + ZERO_PAGE(0), pages[i], + blocksize, offset, GFP_NOFS); + if (err) + goto out; + lblk++; + pblk++; + len--; + offset += blocksize; + if (offset == PAGE_SIZE || len == 0) { + ret = bio_add_page(bio, pages[i++], offset, 0); + if (WARN_ON(ret != offset)) { + err = -EIO; + goto out; + } + offset = 0; + } + } while (i != nr_pages && len != 0); + + err = submit_bio_wait(bio); + if (err) + goto out; + bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE); + } while (len != 0); + err = 0; +out: + bio_put(bio); + for (i = 0; i < nr_pages; i++) + fscrypt_free_bounce_page(pages[i]); + return err; +} +EXPORT_SYMBOL(fscrypt_zeroout_range); |