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Date:   Sat, 25 Mar 2017 10:10:42 +0800
From:   "Gao Feng" <gfree.wind@...mail.com>
To:     "'Pablo Neira Ayuso'" <pablo@...filter.org>
Cc:     <davem@...emloft.net>, <jolsa@...hat.com>,
        <netfilter-devel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <gfree.wind@...il.com>
Subject: RE: [PATCH nf v3 1/1] netfilter: snmp: Fix one possible panic when snmp_trap_helper fail to register

> -----Original Message-----
> From: Pablo Neira Ayuso [mailto:pablo@...filter.org]
> Sent: Saturday, March 25, 2017 3:02 AM
> To: fgao@...ai8.com
> Cc: davem@...emloft.net; jolsa@...hat.com;
netfilter-devel@...r.kernel.org;
> netdev@...r.kernel.org; gfree.wind@...il.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@...ai8.com wrote:
> > From: Gao Feng <fgao@...ai8.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@...ai8.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);
>  }

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