[PATCH net 1/2] wireguard: device: fix metadata_dst xmit null pointer dereference

[Daniel Borkmann]

On 4/14/22 12:44 PM, Nikolay Aleksandrov wrote:
> When we try to transmit an skb with md_dst attached through wireguard
> we hit a null pointer dereference[1] in wg_xmit() due to the use of
> dst_mtu() which calls into dst_blackhole_mtu() which in turn tries to
> dereference dst->dev. Since wireguard doesn't use md_dsts we should use
> skb_valid_dst() which checks for DST_METADATA flag and if it's set then
> fallback to wireguard's device mtu. That gives us the best chance of
> transmitting the packet, otherwise if the blackhole netdev is used we'd
> get ETH_MIN_MTU.
> 
[...]
> 
> CC: stable at vger.kernel.org
> CC: wireguard at lists.zx2c4.com
> CC: Jason A. Donenfeld <Jason at zx2c4.com>
> CC: Daniel Borkmann <daniel at iogearbox.net>
> CC: Martynas Pumputis <m at lambda.lt>
> Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
> Reported-by: Martynas Pumputis <m at lambda.lt>
> Signed-off-by: Nikolay Aleksandrov <razor at blackwall.org>

Looks good to me, thanks Nik!

Acked-by: Daniel Borkmann <daniel at iogearbox.net>