Re: [PATCH net v2] mac802154: llsec: reject frames shorter than the authentication tag

[Breno Leitao <leitao@debian.org>]

On Thu, Jul 16, 2026 at 09:31:06PM +0200, Doruk Tan Ozturk wrote:
> llsec_do_decrypt_auth() computes the associated-data length for the
> AEAD request as
> 
> 	assoclen += datalen - authlen;
> 
> where datalen is the number of bytes after the MAC header and authlen
> (4, 8 or 16) is the length of the authentication tag. Nothing verifies
> that the frame actually carries at least authlen payload bytes. A
> secured frame whose payload is shorter than the tag makes
> datalen - authlen negative; assoclen is then passed to
> aead_request_set_ad() as an unsigned value close to 4 GiB, so
> crypto_aead_decrypt() walks far off the end of the scatterlist that
> only spans the real frame.
> 
> The frame is fully attacker-controlled and reaches this path from any
> IEEE 802.15.4 peer in radio range. Reject frames whose payload is
> shorter than the authentication tag before the subtraction.
> 
> Dynamically reproduced on a KASAN kernel as a general-protection-fault
> in the AEAD scatterwalk, and the fix confirmed.
> 
> Fixes: 4c14a2fb5d14 ("mac802154: add llsec decryption method")
> Cc: stable@vger.kernel.org
> Assisted-by: 0sec:multi-model
> Reviewed-by: Simon Horman <horms@kernel.org>
> Signed-off-by: Doruk Tan Ozturk <doruk@0sec.ai>

Reviwed-by: Breno Leitao <leitao@debian.org>