From: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Date: Mon, 16 Oct 2017 17:09:53 +0200
> From: Johannes Berg <johannes.berg@xxxxxxxxx>
>
> It seems that it's possible to toggle NETLINK_F_EXT_ACK
> through setsockopt() while another thread/CPU is building
> a message inside netlink_ack(), which could then trigger
> the WARN_ON()s I added since if it goes from being turned
> off to being turned on between allocating and filling the
> message, the skb could end up being too small.
>
> Avoid this whole situation by storing the value of this
> flag in a separate variable and using that throughout the
> function instead.
>
> Fixes: 2d4bc93368f5 ("netlink: extended ACK reporting")
> Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Applied and queued up for -stable.
