[Cake] Re: [PATCH net 1/1] net/sched: sch_cake: validate 6in4 inner headers

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 28 Jul 2026 12:44:16 +0200 Toke Høiland-Jørgensen wrote:
> > A malformed packet can therefore use an inner header with a non-IPv6
> > version while still setting the byte used as nexthdr to TCP. When two
> > packets from the same queued flow reach cake_ack_filter(), the version
> > dispatch can fall through to WARN_ON(1), which becomes a denial of
> > service on kernels with panic_on_warn enabled.  
> 
> Hmm, I seem to recall a policy that says we don't care about
> panic_on_warn-induced crashes? What say the maintainers?

Maybe in cases were it's triggered by root doing something stupid.
But packet triggered WARN will definitely cause eyebrows to shift
upwards.

> That being said, I am not sure an unconditional WARN_ON really serves
> any purpose here? As you've shown, this will most likely just be caused
> by malformed packets.
> 
> So rather than add all these new checks, how about we just get rid of
> the WARN_ON?

👍️