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195 lines
5.7 KiB
195 lines
5.7 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Utility functions for file contents encryption/decryption on |
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* block device-based filesystems. |
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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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#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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/** |
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* fscrypt_decrypt_bio() - decrypt the contents of a bio |
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* @bio: the bio to decrypt |
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* |
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* Decrypt the contents of a "read" bio following successful completion of the |
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* underlying disk read. The bio must be reading a whole number of blocks of an |
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* encrypted file directly into the page cache. If the bio is reading the |
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* ciphertext into bounce pages instead of the page cache (for example, because |
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* the file is also compressed, so decompression is required after decryption), |
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* then this function isn't applicable. This function may sleep, so it must be |
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* called from a workqueue rather than from the bio's bi_end_io callback. |
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* |
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* Return: %true on success; %false on failure. On failure, bio->bi_status is |
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* also set to an error status. |
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*/ |
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bool 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 err = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len, |
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bv->bv_offset); |
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if (err) { |
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bio->bi_status = errno_to_blk_status(err); |
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return false; |
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} |
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} |
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return true; |
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} |
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EXPORT_SYMBOL(fscrypt_decrypt_bio); |
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static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode, |
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pgoff_t lblk, sector_t pblk, |
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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 blocks_per_page = 1 << (PAGE_SHIFT - blockbits); |
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struct bio *bio; |
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int ret, err = 0; |
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int num_pages = 0; |
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/* This always succeeds since __GFP_DIRECT_RECLAIM is set. */ |
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bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE, |
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GFP_NOFS); |
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while (len) { |
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unsigned int blocks_this_page = min(len, blocks_per_page); |
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unsigned int bytes_this_page = blocks_this_page << blockbits; |
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if (num_pages == 0) { |
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fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS); |
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bio->bi_iter.bi_sector = |
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pblk << (blockbits - SECTOR_SHIFT); |
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} |
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ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0); |
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if (WARN_ON(ret != bytes_this_page)) { |
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err = -EIO; |
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goto out; |
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} |
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num_pages++; |
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len -= blocks_this_page; |
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lblk += blocks_this_page; |
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pblk += blocks_this_page; |
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if (num_pages == BIO_MAX_VECS || !len || |
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!fscrypt_mergeable_bio(bio, inode, lblk)) { |
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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, inode->i_sb->s_bdev, REQ_OP_WRITE); |
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num_pages = 0; |
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} |
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} |
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out: |
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bio_put(bio); |
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return err; |
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} |
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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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if (fscrypt_inode_uses_inline_crypto(inode)) |
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return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk, |
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len); |
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BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS); |
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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(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS); |
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do { |
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bio->bi_iter.bi_sector = pblk << (blockbits - 9); |
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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, inode->i_sb->s_bdev, REQ_OP_WRITE); |
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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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