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Re: net/icmp: null-ptr-deref in icmp6_send

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> On Nov 22, 2016, at 1:11 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> 
>> On Tue, Nov 22, 2016 at 2:23 AM, Andrey Konovalov <andreyknvl@google.com> wrote:
>> Hi,
>> 
>> I've got the following error report while fuzzing the kernel with syzkaller.
>> 
>> It seems that skb_dst(skb) may end up being NULL.
>> 
>> As far as I can see the bug was introduced in commit 5d41ce29e ("net:
>> icmp6_send should use dst dev to determine L3 domain").
>> ICMP v4 probaly has similar issue due to 9d1a6c4ea ("net:
>> icmp_route_lookup should use rt dev to determine L3 domain").
> 
> 
> ipv6_parse_hopopts() is called before NF_INET_PRE_ROUTING,
> so the skb_dst could be NULL.
> 
> I have no idea what commit 5d41ce29e tried to fix, but we already
> use skb->dev a few lines before l3mdev_master_ifindex(), so I don't
> understand why skb->dev could be NULL, maybe just for vrf dev?

On PTO this week and currently at the beach. Will take a look tonight. Thanks for the report. 

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net/icmp: null-ptr-deref in icmp6_send Andrey Konovalov <andreyknvl@google.com> - 2016-11-22 11:30 +0100
  Re: net/icmp: null-ptr-deref in icmp6_send Cong Wang <xiyou.wangcong@gmail.com> - 2016-11-22 19:20 +0100
    Re: net/icmp: null-ptr-deref in icmp6_send David Ahern <dsa@cumulusnetworks.com> - 2016-11-22 20:20 +0100
    Re: net/icmp: null-ptr-deref in icmp6_send David Ahern <dsa@cumulusnetworks.com> - 2016-11-23 04:20 +0100

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