On Tue, 10 Sep 2024, Eric Biggers wrote:
> From: Eric Biggers <ebigg...@google.com>
>
> sb_mac() verifies that the superblock + MAC don't exceed 512 bytes.
> Because the superblock is currently 64 bytes, this really verifies
> mac_size <= 448. This confuses smatch into thinking that mac_size may
> be as large as 448, which is inconsistent with the later code that
> assumes the MAC fits in a buffer of size HASH_MAX_DIGESTSIZE (64).
>
> In fact mac_size <= HASH_MAX_DIGESTSIZE is guaranteed by the crypto API,
> as that is the whole point of HASH_MAX_DIGESTSIZE. But, let's be
> defensive and explicitly check for this. This suppresses the false
> positive smatch warning. It does not fix an actual bug.
>
> Reported-by: kernel test robot <l...@intel.com>
> Reported-by: Dan Carpenter <dan.carpen...@linaro.org>
> Closes: https://lore.kernel.org/r/202409061401.44rtn1bh-...@intel.com/
> Signed-off-by: Eric Biggers <ebigg...@google.com>
> ---
> drivers/md/dm-integrity.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
> index 51e6964c13054..3b9738787c855 100644
> --- a/drivers/md/dm-integrity.c
> +++ b/drivers/md/dm-integrity.c
> @@ -489,11 +489,12 @@ static int sb_mac(struct dm_integrity_c *ic, bool wr)
> int r;
> unsigned int mac_size = crypto_shash_digestsize(ic->journal_mac);
> __u8 *sb = (__u8 *)ic->sb;
> __u8 *mac = sb + (1 << SECTOR_SHIFT) - mac_size;
>
> - if (sizeof(struct superblock) + mac_size > 1 << SECTOR_SHIFT) {
> + if (sizeof(struct superblock) + mac_size > 1 << SECTOR_SHIFT ||
> + mac_size > HASH_MAX_DIGESTSIZE) {
> dm_integrity_io_error(ic, "digest is too long", -EINVAL);
> return -EINVAL;
> }
>
> desc->tfm = ic->journal_mac;
>
> base-commit: 8d8d276ba2fb5f9ac4984f5c10ae60858090babc
> --
> 2.46.0
I applied the patch.
Mikulas
