macvtap: make sure neighbour code can push ethernet header
Brian reported crashes using IPv6 traffic with macvtap/veth combo.
I tracked the crashes in neigh_hh_output()
-> memcpy(skb->data - HH_DATA_MOD, hh->hh_data, HH_DATA_MOD);
Neighbour code assumes headroom to push Ethernet header is
at least 16 bytes.
It appears macvtap has only 14 bytes available on arches
where NET_IP_ALIGN is 0 (like x86)
Effect is a corruption of 2 bytes right before skb->head,
and possible crashes if accessing non existing memory.
This fix should also increase IPv4 performance, as paranoid code
in ip_finish_output2() wont have to call skb_realloc_headroom()
Reported-by: Brian Rak <brak@vultr.com>
Tested-by: Brian Rak <brak@vultr.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed