Re: [PATCH net v2] netlink: check for null extack in cookie helpers

[David Miller]

From: Michal Kubecek <mkubecek@xxxxxxx>
Date: Sat, 21 Mar 2020 00:46:50 +0100 (CET)

> Unlike NL_SET_ERR_* macros, nl_set_extack_cookie_u64() and
> nl_set_extack_cookie_u32() helpers do not check extack argument for null
> and neither do their callers, as syzbot recently discovered for
> ethnl_parse_header().
> 
> Instead of fixing the callers and leaving the trap in place, add check of
> null extack to both helpers to make them consistent with NL_SET_ERR_*
> macros.
> 
> v2: drop incorrect second Fixes tag
> 
> Fixes: 2363d73a2f3e ("ethtool: reject unrecognized request flags")
> Reported-by: syzbot+258a9089477493cea67b@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>

Applied, thanks Michal.