Re: [PATCH 5/7] netfilter: ebtables: add CONFIG_COMPAT support

[Florian Westphal <fw@strlen.de>]

Florian Westphal <fw@strlen.de> wrote:
> remaining problem:
> 
> The ebtables userland makefile has:
> ifeq ($(shell uname -m),sparc64)
> 	CFLAGS+=-DEBT_MIN_ALIGN=8 -DKERNEL_64_USERSPACE_32
> endif
> 
> struct ebt_replace, ebt_entry_match etc. then contain userland-side
> padding -- this means, if this is actually used in production --
> that even if we are called from a 32 bit userland, the structures
> may already be in the right format.
> 
> One possible solution would be to try to handle compat_* calls via
> the native handler and then fall back to the compat one if it fails,
> but it will cause kernel warnings like:
> kernel msg: ebtables bug: please report to author: Wrong size
> 
> Thus this is not done here.
> 
> I am not sure if this "userland-padding" is widely used; it looks
> incomplete (eg. I couldn't find any
> userland-padding for match/target structures; and some (eg. mark)
> do need special handling).

Just for the record:

Jan Engelhardt was so kind to try "-j mark" with the 32bit
sparc ebtables userland and reported that it is not working.

So I am not sure if I should bother with supporting the "already padded"
userland scenario, as it won't work in some cases anyway.