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

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Message-ID: <20241209222054.GB4709@breakpoint.cc>
Date: Mon, 9 Dec 2024 23:20:54 +0100
From: Florian Westphal <fw@...len.de>
To: Karol Przybylski <karprzy7@...il.com>
Cc: netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, skhan@...uxfoundation.org,
	casey@...aufler-ca.com
Subject: Re: [PATCH] netfilter: nfnetlink_queue: Fix redundant comparison of
 unsigned value

Karol Przybylski <karprzy7@...il.com> wrote:

[ CC original patch author and mass-trimming CCs ]

> 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)
>  			size += nla_total_size(seclen);

Casey, can you please have a look?

AFAICS security_secid_to_secctx() could return -EFOO, so it seems
nfqnl_get_sk_secctx has a bug and should conceal < 0 retvals
(the function returns u32), in addition to the always-true >= check
fixup.