Re: [PATCH net-next 5/8] netfilter: nf_tables: Introduce NFTA_DEVICE_PREFIX

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Sep 01, 2025 at 01:46:02PM -0700, Jakub Kicinski wrote:
> On Mon,  1 Sep 2025 10:08:39 +0200 Florian Westphal wrote:
> > This new attribute is supposed to be used instead of NFTA_DEVICE_NAME
> > for simple wildcard interface specs. It holds a NUL-terminated string
> > representing an interface name prefix to match on.
> > 
> > While kernel code to distinguish full names from prefixes in
> > NFTA_DEVICE_NAME is simpler than this solution, reusing the existing
> > attribute with different semantics leads to confusion between different
> > versions of kernel and user space though:
> > 
> > * With old kernels, wildcards submitted by user space are accepted yet
> >   silently treated as regular names.
> > * With old user space, wildcards submitted by kernel may cause crashes
> >   since libnftnl expects NUL-termination when there is none.
> > 
> > Using a distinct attribute type sanitizes these situations as the
> > receiving part detects and rejects the unexpected attribute nested in
> > *_HOOK_DEVS attributes.
> > 
> > Fixes: 6d07a289504a ("netfilter: nf_tables: Support wildcard netdev hook specs")
> 
> Why is this not targeting net? The sooner we adjust the uAPI the better.

I think there were doubts that was possible at this stage.

But I agree, it is a bit late but better fix it there.

Florian?