linux-kernel - Re: [netfilter-core] [PATCH] net: netfilter: fix GCC uninitialized warning

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Date:	Fri, 6 Nov 2015 20:07:05 +0100
From:	Florian Westphal <fw@...len.de>
To:	Pablo Neira Ayuso <pablo@...filter.org>
Cc:	Dmitry Safonov <0x7f454c46@...il.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kaber@...sh.net,
	coreteam@...filter.org, netfilter-devel@...r.kernel.org,
	kadlec@...ckhole.kfki.hu, davem@...emloft.net
Subject: Re: [netfilter-core] [PATCH] net: netfilter: fix GCC uninitialized
 warning

Pablo Neira Ayuso <pablo@...filter.org> wrote:
> On Fri, Nov 06, 2015 at 09:48:14PM +0300, Dmitry Safonov wrote:
> > With x86_64_defconfig:
> > GCC thinks that in nfulnl_recv_config flags parameter is not inited but
> > it was under the same condition (nfula[NFULA_CFG_FLAGS] == true).
> > Suppress this warning:
> > 	net/netfilter/nfnetlink_log.c: In function ‘nfulnl_recv_config’:
> > 	net/netfilter/nfnetlink_log.c:320:14: warning: ‘flags’ may be used uninitialized in this function [-Wmaybe-uninitialized]
> >   	inst->flags = flags;
> > 	            ^
> > Signed-off-by: Dmitry Safonov <0x7f454c46@...il.com>
> > ---
> >  net/netfilter/nfnetlink_log.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
> > index 06eb48fceb42e4..d65f3b987b7f13 100644
> > --- a/net/netfilter/nfnetlink_log.c
> > +++ b/net/netfilter/nfnetlink_log.c
> > @@ -825,7 +825,7 @@ nfulnl_recv_config(struct sock *ctnl, struct sk_buff *skb,
> >  	struct net *net = sock_net(ctnl);
> >  	struct nfnl_log_net *log = nfnl_log_pernet(net);
> >  	int ret = 0;
> > -	u16 flags;
> > +	u16 flags = 0; /* GCC uninitialized */
> 
>         u16 uninitialized_var(flags); ?

I also see warnings in nfqueue:

net/netfilter/nfnetlink_queue.c:1083:11: warning: 'nfnl_ct' may be used uninitialized in this function [-Wmaybe-uninitialized]
net/netfilter/nfnetlink_queue.c:519:19: warning: 'nfnl_ct' may be used uninitialized in this function [-Wmaybe-uninitialized]

Both are false positives, but it would be nice if we could silence
these.
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