[PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

[PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

[fgao]

From: Gao Feng <fgao@ikuai8.com>

In the commit 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack snmp
helper"), the snmp_helper is replaced by nf_nat_snmp_hook. So the
snmp_helper is never registered. But it still tries to unregister the
snmp_helper, it could cause the panic.

Now remove the useless snmp_helper and the unregister call in the
error handler.

Fixes: 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack snmp helper")

Signed-off-by: Gao Feng <fgao@ikuai8.com>
---
 v3: Remove the angle brackets in description, per Sergei
 v2: Add the SHA1 ID in the description, per Sergei
 v1: Initial version

 net/ipv4/netfilter/nf_nat_snmp_basic.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c b/net/ipv4/netfilter/nf_nat_snmp_basic.c
index c9b52c3..5787364 100644
--- a/net/ipv4/netfilter/nf_nat_snmp_basic.c
+++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c
@@ -1260,16 +1260,6 @@ static int help(struct sk_buff *skb, unsigned int protoff,
 	.timeout	= 180,
 };
 
-static struct nf_conntrack_helper snmp_helper __read_mostly = {
-	.me			= THIS_MODULE,
-	.help			= help,
-	.expect_policy		= &snmp_exp_policy,
-	.name			= "snmp",
-	.tuple.src.l3num	= AF_INET,
-	.tuple.src.u.udp.port	= cpu_to_be16(SNMP_PORT),
-	.tuple.dst.protonum	= IPPROTO_UDP,
-};
-
 static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
 	.me			= THIS_MODULE,
 	.help			= help,
@@ -1294,10 +1284,8 @@ static int __init nf_nat_snmp_basic_init(void)
 	RCU_INIT_POINTER(nf_nat_snmp_hook, help);
 
 	ret = nf_conntrack_helper_register(&snmp_trap_helper);
-	if (ret < 0) {
-		nf_conntrack_helper_unregister(&snmp_helper);
+	if (ret < 0)
 		return ret;
-	}
 	return ret;
 }
 
-- 
1.9.1

Re: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

[Pablo Neira Ayuso]

On Tue, Mar 21, 2017 at 08:22:29AM +0800, fgao@ikuai8.com wrote:
> From: Gao Feng <fgao@ikuai8.com>
> 
> In the commit 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack snmp
> helper"), the snmp_helper is replaced by nf_nat_snmp_hook. So the
> snmp_helper is never registered. But it still tries to unregister the
> snmp_helper, it could cause the panic.

This patch looks correct to me.

But probably for some reason I don't manage to trigger, how do you
reproduce this?

Re: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

[Pablo Neira Ayuso]

On Fri, Mar 24, 2017 at 01:21:30PM +0100, Pablo Neira Ayuso wrote:
> On Tue, Mar 21, 2017 at 08:22:29AM +0800, fgao@ikuai8.com wrote:
> > From: Gao Feng <fgao@ikuai8.com>
> > 
> > In the commit 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack snmp
> > helper"), the snmp_helper is replaced by nf_nat_snmp_hook. So the
> > snmp_helper is never registered. But it still tries to unregister the
> > snmp_helper, it could cause the panic.
> 
> This patch looks correct to me.
> 
> But probably for some reason I don't manage to trigger, how do you
> reproduce this?

I'm refering to the panic.

RE: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

[Gao Feng]

Hi Pablo,

> -----Original Message-----
> From: netfilter-devel-owner@vger.kernel.org
> [mailto:netfilter-devel-owner@vger.kernel.org] On Behalf Of Pablo Neira
Ayuso
> Sent: Friday, March 24, 2017 8:23 PM
> To: fgao@ikuai8.com
> Cc: davem@davemloft.net; jolsa@redhat.com;
netfilter-devel@vger.kernel.org;
> netdev@vger.kernel.org; gfree.wind@gmail.com
> Subject: Re: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic
when
> snmp_trap_helper fail to register
> 
> On Fri, Mar 24, 2017 at 01:21:30PM +0100, Pablo Neira Ayuso wrote:
> > On Tue, Mar 21, 2017 at 08:22:29AM +0800, fgao@ikuai8.com wrote:
> > > From: Gao Feng <fgao@ikuai8.com>
> > >
> > > In the commit 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack
> > > snmp helper"), the snmp_helper is replaced by nf_nat_snmp_hook. So
> > > the snmp_helper is never registered. But it still tries to
> > > unregister the snmp_helper, it could cause the panic.
> >
> > This patch looks correct to me.
> >
> > But probably for some reason I don't manage to trigger, how do you
> > reproduce this?
> 
> I'm refering to the panic.
[高峰] 
It is got by reviewing the codes.
When nf_conntrack_helper_unregister(&snmp_helper), but snmp_helper didn't
register actually.
And snmp_helper. hnode is not initialized, it would trigger the issue when
hlist_del_rcu in nf_conntrack_helper_unregister.

Best Regards
Feng


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Re: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

[Pablo Neira Ayuso]

On Tue, Mar 21, 2017 at 08:22:29AM +0800, fgao@ikuai8.com wrote:
> From: Gao Feng <fgao@ikuai8.com>
> 
> In the commit 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack snmp
> helper"), the snmp_helper is replaced by nf_nat_snmp_hook. So the
> snmp_helper is never registered. But it still tries to unregister the
> snmp_helper, it could cause the panic.
> 
> Now remove the useless snmp_helper and the unregister call in the
> error handler.
> 
> Fixes: 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack snmp helper")
> 
> Signed-off-by: Gao Feng <fgao@ikuai8.com>
> ---
>  v3: Remove the angle brackets in description, per Sergei
>  v2: Add the SHA1 ID in the description, per Sergei
>  v1: Initial version
> 
>  net/ipv4/netfilter/nf_nat_snmp_basic.c | 14 +-------------
>  1 file changed, 1 insertion(+), 13 deletions(-)
> 
> diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c b/net/ipv4/netfilter/nf_nat_snmp_basic.c
> index c9b52c3..5787364 100644
> --- a/net/ipv4/netfilter/nf_nat_snmp_basic.c
> +++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c
> @@ -1260,16 +1260,6 @@ static int help(struct sk_buff *skb, unsigned int protoff,
>  	.timeout	= 180,
>  };
>  
> -static struct nf_conntrack_helper snmp_helper __read_mostly = {
> -	.me			= THIS_MODULE,
> -	.help			= help,
> -	.expect_policy		= &snmp_exp_policy,
> -	.name			= "snmp",
> -	.tuple.src.l3num	= AF_INET,
> -	.tuple.src.u.udp.port	= cpu_to_be16(SNMP_PORT),
> -	.tuple.dst.protonum	= IPPROTO_UDP,
> -};
> -
>  static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
>  	.me			= THIS_MODULE,
>  	.help			= help,
> @@ -1294,10 +1284,8 @@ static int __init nf_nat_snmp_basic_init(void)
>  	RCU_INIT_POINTER(nf_nat_snmp_hook, help);
>  
>  	ret = nf_conntrack_helper_register(&snmp_trap_helper);
> -	if (ret < 0) {
> -		nf_conntrack_helper_unregister(&snmp_helper);
> +	if (ret < 0)
>  		return ret;
> -	}
>  	return ret;

You can provide a more simplified version after this is removed, I
think:

@@ -1283,10 +1283,7 @@ static int __init nf_nat_snmp_basic_init(void)
        BUG_ON(nf_nat_snmp_hook != NULL);
        RCU_INIT_POINTER(nf_nat_snmp_hook, help);
 
-       ret = nf_conntrack_helper_register(&snmp_trap_helper);
-       if (ret < 0)
-               return ret;
-       return ret;
+       return nf_conntrack_helper_register(&snmp_trap_helper);
 }

RE: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

[Gao Feng]

> -----Original Message-----
> From: Pablo Neira Ayuso [mailto:pablo@netfilter.org]
> Sent: Saturday, March 25, 2017 3:02 AM
> To: fgao@ikuai8.com
> Cc: davem@davemloft.net; jolsa@redhat.com;
netfilter-devel@vger.kernel.org;
> netdev@vger.kernel.org; gfree.wind@gmail.com
> Subject: Re: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic
when
> snmp_trap_helper fail to register
> 
> On Tue, Mar 21, 2017 at 08:22:29AM +0800, fgao@ikuai8.com wrote:
> > From: Gao Feng <fgao@ikuai8.com>
> >
> > In the commit 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack
> > snmp helper"), the snmp_helper is replaced by nf_nat_snmp_hook. So the
> > snmp_helper is never registered. But it still tries to unregister the
> > snmp_helper, it could cause the panic.
> >
> > Now remove the useless snmp_helper and the unregister call in the
> > error handler.
> >
> > Fixes: 93557f53e1fb ("netfilter: nf_conntrack: nf_conntrack snmp
> > helper")
> >
> > Signed-off-by: Gao Feng <fgao@ikuai8.com>
> > ---
> >  v3: Remove the angle brackets in description, per Sergei
> >  v2: Add the SHA1 ID in the description, per Sergei
> >  v1: Initial version
> >
> >  net/ipv4/netfilter/nf_nat_snmp_basic.c | 14 +-------------
> >  1 file changed, 1 insertion(+), 13 deletions(-)
> >
> > diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c
> > b/net/ipv4/netfilter/nf_nat_snmp_basic.c
> > index c9b52c3..5787364 100644
> > --- a/net/ipv4/netfilter/nf_nat_snmp_basic.c
> > +++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c
> > @@ -1260,16 +1260,6 @@ static int help(struct sk_buff *skb, unsigned int
> protoff,
> >  	.timeout	= 180,
> >  };
> >
> > -static struct nf_conntrack_helper snmp_helper __read_mostly = {
> > -	.me			= THIS_MODULE,
> > -	.help			= help,
> > -	.expect_policy		= &snmp_exp_policy,
> > -	.name			= "snmp",
> > -	.tuple.src.l3num	= AF_INET,
> > -	.tuple.src.u.udp.port	= cpu_to_be16(SNMP_PORT),
> > -	.tuple.dst.protonum	= IPPROTO_UDP,
> > -};
> > -
> >  static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
> >  	.me			= THIS_MODULE,
> >  	.help			= help,
> > @@ -1294,10 +1284,8 @@ static int __init nf_nat_snmp_basic_init(void)
> >  	RCU_INIT_POINTER(nf_nat_snmp_hook, help);
> >
> >  	ret = nf_conntrack_helper_register(&snmp_trap_helper);
> > -	if (ret < 0) {
> > -		nf_conntrack_helper_unregister(&snmp_helper);
> > +	if (ret < 0)
> >  		return ret;
> > -	}
> >  	return ret;
> 
> You can provide a more simplified version after this is removed, I
> think:
Ok. I thought it should not change the style for bug fix.
I would sent the update patch.

Best Regards
Feng

> 
> @@ -1283,10 +1283,7 @@ static int __init nf_nat_snmp_basic_init(void)
>         BUG_ON(nf_nat_snmp_hook != NULL);
>         RCU_INIT_POINTER(nf_nat_snmp_hook, help);
> 
> -       ret = nf_conntrack_helper_register(&snmp_trap_helper);
> -       if (ret < 0)
> -               return ret;
> -       return ret;
> +       return nf_conntrack_helper_register(&snmp_trap_helper);
>  }