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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Hangbin Liu <liuhangbin@gmail.com>
Cc: netdev@vger.kernel.org, Stefano Brivio <sbrivio@redhat.com>,
	wenxu <wenxu@ucloud.cn>, Alexei Starovoitov <ast@fb.com>,
	"David S . Miller" <davem@davemloft.net>
Subject: Re: [PATCH net] tunnel: fix dev null pointer dereference when send pkg larger than mtu in collect_md mode
Date: Fri, 16 Aug 2019 10:23:55 +0200
Message-ID: <fe103dee-bba8-1e0d-83b2-f91c2c37089d@gmail.com> (raw)
In-Reply-To: <20190816032418.GX18865@dhcp-12-139.nay.redhat.com>



On 8/16/19 5:24 AM, Hangbin Liu wrote:
> Hi Eric,
> 
> Thanks for the review.
> On Thu, Aug 15, 2019 at 11:16:58AM +0200, Eric Dumazet wrote:
>>> diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
>>> index 38c02bb62e2c..c6713c7287df 100644
>>> --- a/net/ipv4/ip_tunnel.c
>>> +++ b/net/ipv4/ip_tunnel.c
>>> @@ -597,6 +597,9 @@ void ip_md_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
>>>  		goto tx_error;
>>>  	}
>>>  
>>> +	if (skb_dst(skb) && !skb_dst(skb)->dev)
>>> +		skb_dst(skb)->dev = rt->dst.dev;
>>> +
>>
>>
>> IMO this looks wrong.
>> This dst seems shared. 
> 
> If the dst is shared, it may cause some problem. Could you point me where the
> dst may be shared possibly?
>

dst are inherently shared.

This is why we have a refcount on them.

Only when the dst has been allocated by the current thread we can make changes on them.


  parent reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-15  6:09 Hangbin Liu
2019-08-15  9:16 ` Eric Dumazet
2019-08-16  3:24   ` Hangbin Liu
2019-08-16  4:01     ` Hangbin Liu
2019-08-16  8:23     ` Eric Dumazet [this message]
2019-08-16 10:51       ` Hangbin Liu
2019-08-19  7:53 ` [PATCHv2 0/2] " Hangbin Liu
2019-08-19  7:53   ` [PATCH 1/2] ipv4/icmp: fix rt dst dev null pointer dereference Hangbin Liu
2019-08-21 16:11     ` Julian Anastasov
2019-08-19  7:53   ` [PATCH 2/2] xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode Hangbin Liu
2019-08-20 19:20   ` [PATCHv2 0/2] fix dev null pointer dereference when send pkg larger than mtu " David Miller
2019-08-21  2:09 ` [PATCHv3 0/2] fix dev null pointer dereference when send packets " Hangbin Liu
2019-08-21  2:09   ` [PATCHv3 1/2] ipv4/icmp: fix rt dst dev null pointer dereference Hangbin Liu
2019-08-21  2:09   ` [PATCHv3 2/2] xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode Hangbin Liu
2019-08-22 14:19 ` [PATCHv4 0/2] fix dev null pointer dereference when send packets larger than mtu " Hangbin Liu
2019-08-22 14:19   ` [PATCHv4 net 1/2] ipv4/icmp: fix rt dst dev null pointer dereference Hangbin Liu
2019-08-22 18:46     ` Julian Anastasov
2019-08-23 22:32     ` Jonathan Lemon
2019-08-22 14:19   ` [PATCHv4 net 2/2] xfrm/xfrm_policy: fix dst dev null pointer dereference in collect_md mode Hangbin Liu
2019-08-23 22:30     ` Jonathan Lemon

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