linux-kernel - Re: [PATCH] netfilter: nfnetlink_queue: Fix redundant comparison of unsigned value

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Message-ID: <Z1dnvR1I19Baqjn2@calendula>
Date: Mon, 9 Dec 2024 22:57:17 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: Karol P <karprzy7@...il.com>
Cc: kadlec@...filter.org, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	skhan@...uxfoundation.org
Subject: Re: [PATCH] netfilter: nfnetlink_queue: Fix redundant comparison of
 unsigned value

On Mon, Dec 09, 2024 at 10:50:17PM +0100, Karol P wrote:
> On Mon, 9 Dec 2024 at 22:32, Pablo Neira Ayuso <pablo@...filter.org> wrote:
> >
> > Hi,
> >
> > On Mon, Dec 09, 2024 at 09:49:18PM +0100, Karol Przybylski wrote:
> > > The comparison seclen >= 0 in net/netfilter/nfnetlink_queue.c is redundant because seclen is an unsigned value, and such comparisons are always true.
> > >
> > > This patch removes the unnecessary comparison replacing it with just 'greater than'
> > >
> > > Discovered in coverity, CID 1602243
> > >
> > > Signed-off-by: Karol Przybylski <karprzy7@...il.com>
> > > ---
> > >  net/netfilter/nfnetlink_queue.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
> > > index 5110f29b2..eacb34ffb 100644
> > > --- a/net/netfilter/nfnetlink_queue.c
> > > +++ b/net/netfilter/nfnetlink_queue.c
> > > @@ -643,7 +643,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
> > >
> > >       if ((queue->flags & NFQA_CFG_F_SECCTX) && entskb->sk) {
> > >               seclen = nfqnl_get_sk_secctx(entskb, &ctx);
> > > -             if (seclen >= 0)
> > > +             if (seclen > 0)
> >
> > What tree are you using? I don't see this code in net-next.git
> 
> linux-next, next-20241209
> Link: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/net/netfilter/nfnetlink_queue.c?h=next-20241209#n646

Could you trace from what commit ID and what tree this is coming?

Then, post the patch to the corresponding tree and add a Fixes: tag?

Possibly use:

        if (seclen)

as this code was before?

Thanks.

> > >                       size += nla_total_size(seclen);
> > >       }
> > >
> > > @@ -810,7 +810,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
> > >       }
> > >
> > >       nlh->nlmsg_len = skb->len;
> > > -     if (seclen >= 0)
> > > +     if (seclen > 0)
> > >               security_release_secctx(&ctx);
> > >       return skb;
> > >
> > > @@ -819,7 +819,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
> > >       kfree_skb(skb);
> > >       net_err_ratelimited("nf_queue: error creating packet message\n");
> > >  nlmsg_failure:
> > > -     if (seclen >= 0)
> > > +     if (seclen > 0)
> > >               security_release_secctx(&ctx);
> > >       return NULL;
> > >  }
> > > --
> > > 2.34.1
> > >