Re: RX metadata kfuncs cause kernel panic with XDP generic mode

[Stanislav Fomichev <stfomichev@gmail.com>]

On 01/23, Marcus Wichelmann wrote:
> 
> Am 23.01.25 um 17:38 schrieb Toke Høiland-Jørgensen:
> > Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de> writes:
> > 
> > > There is probably a check missing somewhere that prevents the use of
> > > these kfuncs in the scope of do_xdp_generic?
> > 
> > Heh, yeah, we should definitely block device-bound programs from being
> > attached in generic mode. Something like the below, I guess. Care to
> > test that out?
> > 
> > -Toke
> > 
> Ah, thanks for the quick patch. ;)
> 
> I have tested your patch with the 6.12 branch I'm currently working with and this does the job.
> 
>   # bpftool prog load crash.o /sys/fs/bpf/crash xdpmeta_dev mlx5-conx5-1
>   # bpftool net attach xdpgeneric pinned /sys/fs/bpf/crash dev mlx5-conx5-1
>   libbpf: Kernel error message: Can't attach device-bound programs in generic mode
>   Error: interface xdpgeneric attach failed: Invalid argument
> 
> The do_xdp_generic is also used by the tun driver as a fallback in some cases, so, to my understanding,
> even programs attached in driver-mode may take the generic XDP path. How can this be handled there?

[..]

> Currently, it's not an issue, because the tun driver does not implement the xdp_metadata_ops yet, but
> it may become one in the future.

We can solve it if/when we add metadata_ops to the tun driver, right?
Not sure we need any immediate action right now.