[PATCH] net: netfilter: fix GCC uninitialized warning

[PATCH] net: netfilter: fix GCC uninitialized warning

[Dmitry Safonov]

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@gmail.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 */
 
 	if (nfula[NFULA_CFG_CMD]) {
 		u_int8_t pf = nfmsg->nfgen_family;
-- 
2.6.2

Re: [PATCH] net: netfilter: fix GCC uninitialized warning

[Pablo Neira Ayuso]

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@gmail.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); ?

>  	if (nfula[NFULA_CFG_CMD]) {
>  		u_int8_t pf = nfmsg->nfgen_family;
> -- 
> 2.6.2
> 

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

[Florian Westphal]

Pablo Neira Ayuso <pablo@netfilter.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@gmail.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.

[PATCH] net: netfilter: fix false positive GCC warnings

[Dmitry Safonov]

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;
                    ^
GCC thinks that nfnl_ct wasn't inited, but it is used only under
	if (ct && diff)
where ct is not NULL only when nfnl_ct is inited.

Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com>
---
 net/netfilter/nfnetlink_log.c   | 2 +-
 net/netfilter/nfnetlink_queue.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 06eb48fceb42e4..23f16b99e6388a 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 uninitialized_var(flags);
 
 	if (nfula[NFULA_CFG_CMD]) {
 		u_int8_t pf = nfmsg->nfgen_family;
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 7d81d280cb4ff3..66b006112921ca 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -313,7 +313,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 	struct net_device *outdev;
 	struct nf_conn *ct = NULL;
 	enum ip_conntrack_info uninitialized_var(ctinfo);
-	struct nfnl_ct_hook *nfnl_ct;
+	struct nfnl_ct_hook *uninitialized_var(nfnl_ct);
 	bool csum_verify;
 	char *secdata = NULL;
 	u32 seclen = 0;
@@ -1041,7 +1041,7 @@ nfqnl_recv_verdict(struct sock *ctnl, struct sk_buff *skb,
 	unsigned int verdict;
 	struct nf_queue_entry *entry;
 	enum ip_conntrack_info uninitialized_var(ctinfo);
-	struct nfnl_ct_hook *nfnl_ct;
+	struct nfnl_ct_hook *uninitialized_var(nfnl_ct);
 	struct nf_conn *ct = NULL;
 
 	struct net *net = sock_net(ctnl);
-- 
2.6.2

Re: [PATCH] net: netfilter: fix GCC uninitialized warning

[Dmitry Safonov]

I thought, it was decided to use 0/NULL/whatever, than uninitialized_var()?
Is right now?
http://thread.gmane.org/gmane.linux.kernel/1383415

2015-11-06 22:10 GMT+03:00 Pablo Neira Ayuso <pablo@netfilter.org>:
> 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@gmail.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); ?
>
>>       if (nfula[NFULA_CFG_CMD]) {
>>               u_int8_t pf = nfmsg->nfgen_family;
>> --
>> 2.6.2
>>

Re: [PATCH] net: netfilter: fix GCC uninitialized warning

[Pablo Neira Ayuso]

On Fri, Nov 06, 2015 at 10:13:16PM +0300, Dmitry Safonov wrote:
> I thought, it was decided to use 0/NULL/whatever, than uninitialized_var()?
> Is right now?
> http://thread.gmane.org/gmane.linux.kernel/1383415

I overlook that one. We should stick to mainstream policies as much as
possible.

Arnd just sent a patch to address one of this by initializing the
variable: http://patchwork.ozlabs.org/patch/542259/

Please follow up with a patch to initialize the variable to avoid the
warning in other spots.

Thanks.