netdev - Re:Re: [PATCH net v2] driver: vrf: Fix one possible use-after-free issue

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Date:   Wed, 10 May 2017 09:00:18 +0800 (CST)
From:   "Gao Feng" <gfree.wind@....163.com>
To:     "David Miller" <davem@...emloft.net>
Cc:     dsa@...ulusnetworks.com, shm@...ulusnetworks.com, fw@...len.de,
        netdev@...r.kernel.org
Subject: Re:Re: [PATCH net v2] driver: vrf: Fix one possible use-after-free
 issue


At 2017-05-10 02:37:36, "David Miller" <davem@...emloft.net> wrote:
>From: gfree.wind@....163.com
>Date: Tue,  9 May 2017 18:27:33 +0800
>
>> @@ -989,6 +989,7 @@ static u32 vrf_fib_table(const struct net_device *dev)
>>  
>>  static int vrf_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
>>  {
>> +	kfree_skb(skb);
>>  	return 0;
>>  }
>>  
>> @@ -998,7 +999,7 @@ static struct sk_buff *vrf_rcv_nfhook(u8 pf, unsigned int hook,
>>  {
>>  	struct net *net = dev_net(dev);
>>  
>> -	if (NF_HOOK(pf, hook, net, NULL, skb, dev, NULL, vrf_rcv_finish) < 0)
>> +	if (nf_hook(pf, hook, net, NULL, skb, dev, NULL, vrf_rcv_finish) != 1)
>>  		skb = NULL;    /* kfree_skb(skb) handled by nf code */
>>  
>>  	return skb;
>
>Indeed, this fixes the immediate problem with NF_STOLEN.
>
>Making NF_STOLEN fully functional is another story, we'd need to stack
>this all together properly:

Yes, this fix just make the vrf wouldn't cause panic which is caused by use-after-free skb.
It doesn't work as real NF_QUEUE when reinject the skb. 

>
>static int __ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
>{
> ...
>}
>
>static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
>{
>	return l3mdev_ip_rcv(skb, __ip_rcv_finish);
>}
>...
>static inline
>struct sk_buff *l3mdev_ip_rcv(struct sk_buff *skb,
>			      int (*okfn)(struct net *, struct sock *, struct sk_buff *))
>{
>	return l3mdev_l3_rcv(skb, okfn, AF_INET);
>}
>
>etc. but that's going to really add a kink to the receive path,
>microbenchmark wise.

It is a solution to make NF_STOLEN fully function, but I haven't environment to test the benchmark.

Best Regards
Feng