netdev - Re: [PATCH net 2/2] bareudp: Fix use of incorrect min

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Date:   Sun, 27 Dec 2020 17:33:31 +0100
From:   Guillaume Nault <gnault@...hat.com>
To:     Taehee Yoo <ap420073@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org,
        martin.varghese@...ia.com
Subject: Re: [PATCH net 2/2] bareudp: Fix use of incorrect min_headroom size

On Sat, Dec 26, 2020 at 05:13:08PM +0000, Taehee Yoo wrote:
> In the bareudp6_xmit_skb(), it calculates min_headroom.
> At that point, it uses struct iphdr, but it's not correct.
> So panic could occur.
> The struct ipv6hdr should be used.
> 
> Test commands:
>     ip netns add A
>     ip netns add B
>     ip link add veth0 type veth peer name veth1
>     ip link set veth0 netns A

Missing "ip link set veth1 netns B", so the reproducer unfortunately
doesn't work.

BTW, you can also simplify the script by creating the veth devices
directly in the right netns:
  ip link add name veth0 netns A type veth peer name veth1 netns B

Apart from that,
Acked-by: Guillaume Nault <gnault@...hat.com>

And thanks a lot for the reproducers!

>     ip netns exec A ip link set veth0 up
>     ip netns exec A ip a a 2001:db8:0::1/64 dev veth0
>     ip netns exec B ip link set veth1 up
>     ip netns exec B ip a a 2001:db8:0::2/64 dev veth1
> 
>     for i in {10..1}
>     do
>             let A=$i-1
>             ip netns exec A ip link add bareudp$i type bareudp dstport $i \
> 		    ethertype 0x86dd
>             ip netns exec A ip link set bareudp$i up
>             ip netns exec A ip -6 a a 2001:db8:$i::1/64 dev bareudp$i
>             ip netns exec A ip -6 r a 2001:db8:$i::2 encap ip6 src \
> 		    2001:db8:$A::1 dst 2001:db8:$A::2 via 2001:db8:$i::2 \
> 		    dev bareudp$i
> 
>             ip netns exec B ip link add bareudp$i type bareudp dstport $i \
> 		    ethertype 0x86dd
>             ip netns exec B ip link set bareudp$i up
>             ip netns exec B ip -6 a a 2001:db8:$i::2/64 dev bareudp$i
>             ip netns exec B ip -6 r a 2001:db8:$i::1 encap ip6 src \
> 		    2001:db8:$A::2 dst 2001:db8:$A::1 via 2001:db8:$i::1 \
> 		    dev bareudp$i
>     done
>     ip netns exec A ping 2001:db8:7::2