ath10k: Validate first subframe of A-MSDU before processing the list

ath10k: Validate first subframe of A-MSDU before processing the list

In certain scenarios a normal MSDU can be received as an A-MSDU when
the A-MSDU present bit of a QoS header gets flipped during reception.
Since this bit is unauthenticated, the hardware crypto engine can pass
the frame to the driver without any error indication.

This could result in processing unintended subframes collected in the
A-MSDU list. Hence, validate A-MSDU list by checking if the first frame
has a valid subframe header.

Comparing the non-aggregated MSDU and an A-MSDU, the fields of the first
subframe DA matches the LLC/SNAP header fields of a normal MSDU.
In order to avoid processing such frames, add a validation to
filter such A-MSDU frames where the first subframe header DA matches
with the LLC/SNAP header pattern.

Tested-on: QCA9984 hw1.0 PCI 10.4-3.10-00047

Cc: stable@vger.kernel.org
Signed-off-by: Sriram R <srirrama@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20210511200110.e6f5eb7b9847.I38a77ae26096862527a5eab73caebd7346af8b66@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>