Re: [PATCH net 4/5] openvswitch: use eth_type_trans_careful() in internal_dev_recv()

Eric Dumazet [off-list ref] writes:

OVS actions like pop_eth followed by pop_mpls(ETH_P_TEB) or pop_nsh
can expose an inner Ethernet header which is not in the linear part
of the skb. Output to an internal port then crashes in eth_type_trans():

  flow: in_port(0),eth(),eth_type(0x8847),mpls(lse=0x00010140)
  actions: pop_eth,pop_mpls(0x6558),0
  # AF_PACKET SOCK_RAW on dp0: eth / mpls / eth / 4096 bytes of payload

  kernel BUG at include/linux/skbuff.h:2839!
  RIP: 0010:eth_type_trans (include/linux/etherdevice.h:635 net/ethernet/eth.c:163)
  Call Trace:
   internal_dev_recv (net/openvswitch/vport-internal_dev.c:202) openvswitch
   do_execute_actions (net/openvswitch/actions.c:1296) openvswitch
   ovs_execute_actions (net/openvswitch/actions.c:1606) openvswitch
   ovs_dp_process_packet (net/openvswitch/datapath.c:310) openvswitch
   ovs_vport_receive (net/openvswitch/vport.c:448) openvswitch
   internal_dev_xmit (net/openvswitch/vport-internal_dev.c:42) openvswitch
   dev_hard_start_xmit (include/linux/netdevice.h:5455 include/linux/netdevice.h:5464 net/core/dev.c:4057 net/core/dev.c:4073)
   __dev_queue_xmit (net/core/dev.c:5066)
   packet_sendmsg (net/packet/af_packet.c:3157 net/packet/af_packet.c:3189)

Use eth_type_trans_careful(), and drop the packet if the Ethernet
header can not be pulled. This covers all OVS actions at the consumer,
instead of fixing each producer.

Fixes: b2d0f5d5dc53 ("openvswitch: enable NSH support")
Fixes: f66b53fdbb22 ("openvswitch: New MPLS actions for layer 2 tunnelling")
Signed-off-by: Eric Dumazet <edumazet@kernel.org>
---

Thanks Eric, this looks good to me.  I guess Jamal's proposed changes
for OVS/TC aren't needed with this series.

Reviewed-by: Aaron Conole <aconole@redhat.com>