Re: [PATCH 04/11] dm verity fec: Remove VLA usage

Herbert Xu
2018-06-21T02:31:39Z

On Wed, Jun 20, 2018 at 12:04:01PM -0700, Kees Cook wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this
> uses the newly defined max digest size macro. Also adds a sanity-check
> at use-time.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> drivers/md/dm-verity-fec.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
> index 684af08d0747..0dfcc52835bc 100644
> --- a/drivers/md/dm-verity-fec.c
> +++ b/drivers/md/dm-verity-fec.c
> @@ -212,12 +212,15 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io,
> struct dm_verity_fec_io *fio = fec_io(io);
> u64 block, ileaved;
> u8 *bbuf, *rs_block;
> - u8 want_digest[v->digest_size];
> + u8 want_digest[AHASH_MAX_DIGESTSIZE];
> unsigned n, k;
>
> if (neras)
> *neras = 0;
>
> + if (WARN_ON(v->digest_size < sizeof(want_digest)))
> + return -EINVAL;

How about verifying digest_size in the ahash API when algorithms
are registered?

Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt