linux-kernel - Re: nfnetlink warnings

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Date:	Mon, 23 Nov 2015 10:49:34 +0100
From:	Michael Wang <yun.wang@...fitbricks.com>
To:	Borislav Petkov <bp@...en8.de>,
	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	netfilter-devel@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: nfnetlink warnings

Hi, Borislav

Why not just initialized it as NULL, or mark it as uninitialized_var()?

Regards,
Michael Wang

On 11/23/2015 10:36 AM, Borislav Petkov wrote:
> Hey,
> 
> so I keep getting those since recently:
> 
> net/netfilter/nfnetlink_queue.c:519:19: warning: ‘nfnl_ct’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>   if (ct && nfnl_ct->build(skb, ct, ctinfo, NFQA_CT, NFQA_CT_INFO) < 0)
>                    ^
> net/netfilter/nfnetlink_queue.c:316:23: note: ‘nfnl_ct’ was declared here
>   struct nfnl_ct_hook *nfnl_ct;
>                        ^
> net/netfilter/nfnetlink_queue.c: In function ‘nfqnl_recv_verdict’:
> net/netfilter/nfnetlink_queue.c:1083:11: warning: ‘nfnl_ct’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>     nfnl_ct->seq_adjust(entry->skb, ct, ctinfo, diff);
>            ^
> 
> and was thinking can we shut them up like this? I know, it is ugly :-\
> 
> I mean, it is obvious in both cases that nfnl_ct won't be used if ct is
> not set but apparently gcc can't see that far...
> 
> ---
> diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
> index 7d81d280cb4f..cd61b0b5c413 100644
> --- a/net/netfilter/nfnetlink_queue.c
> +++ b/net/netfilter/nfnetlink_queue.c
> @@ -372,6 +372,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
>  			if (ct != NULL)
>  				size += nfnl_ct->build_size(ct);
>  		}
> +	} else {
> +		nfnl_ct = NULL;
>  	}
>  
>  	if (queue->flags & NFQA_CFG_F_UID_GID) {
> @@ -1069,6 +1071,8 @@ nfqnl_recv_verdict(struct sock *ctnl, struct sk_buff *skb,
>  		nfnl_ct = rcu_dereference(nfnl_ct_hook);
>  		if (nfnl_ct != NULL)
>  			ct = nfqnl_ct_parse(nfnl_ct, nlh, nfqa, entry, &ctinfo);
> +	} else {
> +		nfnl_ct = NULL;
>  	}
>  
>  	if (nfqa[NFQA_PAYLOAD]) {
> 
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