Commit 284d5db5 authored by Eric Biggers's avatar Eric Biggers
Browse files

fsverity: use unsigned long for level_start 



fs/verity/ isn't consistent with whether Merkle tree block indices are
'unsigned long' or 'u64'.  There's no real point to using u64 for them,
though, since (a) a Merkle tree with over ULONG_MAX blocks would only be
needed for a file larger than MAX_LFS_FILESIZE, and (b) for reads, the
status of all Merkle tree blocks has to be tracked in memory.

Therefore, let's make things a bit more efficient on 32-bit systems by
using 'unsigned long[]' for merkle_tree_params::level_start, instead of
'u64[]'.  Also, to be extra safe, explicitly check that there aren't
more than ULONG_MAX Merkle tree blocks.

Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Reviewed-by: default avatarAndrey Albershteyn <aalbersh@redhat.com>
Tested-by: default avatarOjaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://lore.kernel.org/r/20221223203638.41293-2-ebiggers@kernel.org
parent 86f66569

fs/verity/fsverity_private.h

+1 −1
Original line number Diff line number Diff line
@@ -52,7 +52,7 @@ struct merkle_tree_params { 
	 * Starting block index for each tree level, ordered from leaf level (0)

	 * to root level ('num_levels - 1')

	 */

	u64 level_start[FS_VERITY_MAX_LEVELS];

	unsigned long level_start[FS_VERITY_MAX_LEVELS];

};



/*

fs/verity/open.c

+15 −5
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 
	struct fsverity_hash_alg *hash_alg;

	int err;

	u64 blocks;

	u64 blocks_in_level[FS_VERITY_MAX_LEVELS];

	u64 offset;

	int level;
@@ -94,17 +95,26 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 
		}

		blocks = (blocks + params->hashes_per_block - 1) >>

			 params->log_arity;

		/* temporarily using level_start[] to store blocks in level */

		params->level_start[params->num_levels++] = blocks;

		blocks_in_level[params->num_levels++] = blocks;

	}

	params->level0_blocks = params->level_start[0];

	params->level0_blocks = blocks_in_level[0];



	/* Compute the starting block of each level */

	offset = 0;

	for (level = (int)params->num_levels - 1; level >= 0; level--) {

		blocks = params->level_start[level];

		params->level_start[level] = offset;

		offset += blocks;

		offset += blocks_in_level[level];

	}



	/*

	 * Since the data, and thus also the Merkle tree, cannot have more than

	 * ULONG_MAX pages, hash block indices can always fit in an

	 * 'unsigned long'.  To be safe, explicitly check for it too.

	 */

	if (offset > ULONG_MAX) {

		fsverity_err(inode, "Too many blocks in Merkle tree");

		err = -EFBIG;

		goto out_err;

	}



	params->tree_size = offset << log_blocksize;