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![Eric Biggers](/assets/img/avatar_default.png)
Try to make the filesystem-level decryption functions in fs/crypto/ aware of large folios. This includes making fscrypt_decrypt_bio() support the case where the bio contains large folios, and making fscrypt_decrypt_pagecache_blocks() take a folio instead of a page. There's no way to actually test this with large folios yet, but I've tested that this doesn't cause any regressions. Note that this patch just handles *decryption*, not encryption which will be a little more difficult. Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Link: https://lore.kernel.org/r/20230127224202.355629-1-ebiggers@kernel.org
193 lines
5.6 KiB
C
193 lines
5.6 KiB
C
// 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 folio_iter fi;
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bio_for_each_folio_all(fi, bio) {
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int err = fscrypt_decrypt_pagecache_blocks(fi.folio, fi.length,
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fi.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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