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fsverity: use unsigned long for level_start

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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: 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/20221223203638.41293-2-ebiggers@kernel.org
This commit is contained in:
Eric Biggers 2022-12-23 12:36:28 -08:00
parent 86f66569ba
commit 284d5db5f9
2 changed files with 16 additions and 6 deletions
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2
fs/verity/fsverity_private.h
View File

@ -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];
};
/*

20
fs/verity/open.c
View File

@ -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;