Re: [nf-next PATCH] netfilter: include: uapi: Use C99 flexible array member

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

On Fri, Jul 17, 2020 at 12:06:48PM +0200, Phil Sutter wrote:
> Hi Pablo,
> 
> On Wed, Jul 15, 2020 at 08:14:33PM +0200, Pablo Neira Ayuso wrote:
> > On Mon, Jul 13, 2020 at 01:15:52PM +0200, Phil Sutter wrote:
> > [...]
> > > Avoid this warning by declaring 'entries' as an ISO C99 flexible array
> > > member. This makes gcc aware of the intended use and enables sanity
> > > checking as described in:
> > > https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> > > 
> > > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > > ---
> > >  include/uapi/linux/netfilter_ipv4/ip_tables.h  | 2 +-
> > >  include/uapi/linux/netfilter_ipv6/ip6_tables.h | 2 +-
> > >  2 files changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/include/uapi/linux/netfilter_ipv4/ip_tables.h b/include/uapi/linux/netfilter_ipv4/ip_tables.h
> > > index 50c7fee625ae9..1a298cc7a29c1 100644
> > > --- a/include/uapi/linux/netfilter_ipv4/ip_tables.h
> > > +++ b/include/uapi/linux/netfilter_ipv4/ip_tables.h
> > > @@ -203,7 +203,7 @@ struct ipt_replace {
> > >  	struct xt_counters __user *counters;
> > >  
> > >  	/* The entries (hang off end: not really an array). */
> > > -	struct ipt_entry entries[0];
> > > +	struct ipt_entry entries[];
> > 
> > arpt_replace uses this idiom too.
> 
> Oh, indeed. I focussed on those cases gcc complained about when
> compiling iptables. Grepping for '\[0\]' in all of
> include/uapi/linux/netfilter* reveals a few more cases. Do you think
> it's worth "fixing" those as well?

It seems this patch was missing a few spots, right?

commit 6daf14140129d30207ed6a0a69851fa6a3636bda
Author: Gustavo A. R. Silva <gustavo@embeddedor.com>
Date:   Thu Feb 20 07:59:14 2020 -0600

    netfilter: Replace zero-length array with flexible-array member

Probably Cc: Gustavo to confirm this.