netdev - Re: [PATCH net 2/2] net: dev_queue_xmit_nit: fix potential NULL ptr dereference

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Date:	Tue, 08 Jan 2013 20:38:43 +0100
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Changli Gao <xiaosuo@...il.com>
Subject: Re: [PATCH net 2/2] net: dev_queue_xmit_nit: fix potential NULL ptr
 dereference

On 01/08/2013 08:22 PM, Eric Dumazet wrote:
> On Tue, 2013-01-08 at 19:51 +0100, Daniel Borkmann wrote:
>> Commit 71d9dec24dce548bf699815c976cf063ad9257e2 (``net: increase
>> skb->users instead of skb_clone()'') introduced a skb_clone in
>> dev_queue_xmit_nit that, when NULL, leaves the loop, but can still
>> be injected into pt_prev->func().
>>
>> Cc: Changli Gao <xiaosuo@...il.com>
>> Cc: Eric Dumazet <eric.dumazet@...il.com>
>> Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
>> ---
>>   net/core/dev.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 723dcd0..6c35c33 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -1827,7 +1827,7 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev)
>>   			pt_prev = ptype;
>>   		}
>>   	}
>> -	if (pt_prev)
>> +	if (skb2 && pt_prev)
>>   		pt_prev->func(skb2, skb->dev, pt_prev, skb->dev);
>>   	rcu_read_unlock();
>>   }
>
> My opinion is this patch is not needed.
>
> pt_prev can be set only if skb2 is not NULL

Agreed, I missed that, thanks.
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