fsverity: support verification with tree block size < PAGE_SIZE
Add support for verifying data from verity files whose Merkle tree block
size is less than the page size. The main use case for this is to allow
a single Merkle tree block size to be used across all systems, so that
only one set of fsverity file digests and signatures is needed.
To do this, eliminate various assumptions that the Merkle tree block
size and the page size are the same:
- Make fsverity_verify_page() a wrapper around a new function
fsverity_verify_blocks() which verifies one or more blocks in a page.
- When a Merkle tree block is needed, get the corresponding page and
only verify and use the needed portion. (The Merkle tree continues to
be read and cached in page-sized chunks; that doesn't need to change.)
- When the Merkle tree block size and page size differ, use a bitmap
fsverity_info::hash_block_verified to keep track of which Merkle tree
blocks have been verified, as PageChecked cannot be used directly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Andrey Albershteyn <aalbersh@redhat.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-7-ebiggers@kernel.org
5 files changed
