linux/fs/verity/verify.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Data verification functions, i.e. hooks for ->readahead()
 *
 * Copyright 2019 Google LLC
 */

#include "fsverity_private.h"

#include <crypto/hash.h>
#include <linux/bio.h>

static struct workqueue_struct *fsverity_read_workqueue;

/*
 * Returns true if the hash block with index @hblock_idx in the tree, located in
 * @hpage, has already been verified.
 */
static bool is_hash_block_verified(struct fsverity_info *vi, struct page *hpage,
				   unsigned long hblock_idx)
{ … }

/*
 * Verify a single data block against the file's Merkle tree.
 *
 * In principle, we need to verify the entire path to the root node.  However,
 * for efficiency the filesystem may cache the hash blocks.  Therefore we need
 * only ascend the tree until an already-verified hash block is seen, and then
 * verify the path to that block.
 *
 * Return: %true if the data block is valid, else %false.
 */
static bool
verify_data_block(struct inode *inode, struct fsverity_info *vi,
		  const void *data, u64 data_pos, unsigned long max_ra_pages)
{ … }

static bool
verify_data_blocks(struct folio *data_folio, size_t len, size_t offset,
		   unsigned long max_ra_pages)
{ … }

/**
 * fsverity_verify_blocks() - verify data in a folio
 * @folio: the folio containing the data to verify
 * @len: the length of the data to verify in the folio
 * @offset: the offset of the data to verify in the folio
 *
 * Verify data that has just been read from a verity file.  The data must be
 * located in a pagecache folio that is still locked and not yet uptodate.  The
 * length and offset of the data must be Merkle tree block size aligned.
 *
 * Return: %true if the data is valid, else %false.
 */
bool fsverity_verify_blocks(struct folio *folio, size_t len, size_t offset)
{ … }
EXPORT_SYMBOL_GPL(…);

#ifdef CONFIG_BLOCK
/**
 * fsverity_verify_bio() - verify a 'read' bio that has just completed
 * @bio: the bio to verify
 *
 * Verify the bio's data against the file's Merkle tree.  All bio data segments
 * must be aligned to the file's Merkle tree block size.  If any data fails
 * verification, then bio->bi_status is set to an error status.
 *
 * This is a helper function for use by the ->readahead() method of filesystems
 * that issue bios to read data directly into the page cache.  Filesystems that
 * populate the page cache without issuing bios (e.g. non block-based
 * filesystems) must instead call fsverity_verify_page() directly on each page.
 * All filesystems must also call fsverity_verify_page() on holes.
 */
void fsverity_verify_bio(struct bio *bio)
{ … }
EXPORT_SYMBOL_GPL(…);
#endif /* CONFIG_BLOCK */

/**
 * fsverity_enqueue_verify_work() - enqueue work on the fs-verity workqueue
 * @work: the work to enqueue
 *
 * Enqueue verification work for asynchronous processing.
 */
void fsverity_enqueue_verify_work(struct work_struct *work)
{ … }
EXPORT_SYMBOL_GPL(…);

void __init fsverity_init_workqueue(void)
{ … }