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

[Eric Dumazet <edumazet@kernel.org>]

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>
---
 net/openvswitch/vport-internal_dev.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/openvswitch/vport-internal_dev.c b/net/openvswitch/vport-internal_dev.c
index 77a16d5ebd54343c80a2def261aadcb8ff0d1274..8f035087f0eec80eddf6b493cf5ba7915a3e01c6 100644
--- a/net/openvswitch/vport-internal_dev.c
+++ b/net/openvswitch/vport-internal_dev.c
@@ -188,6 +188,7 @@ static void internal_dev_destroy(struct vport *vport)
 static int internal_dev_recv(struct sk_buff *skb)
 {
 	struct net_device *netdev = skb->dev;
+	enum skb_drop_reason reason;
 
 	if (unlikely(!(netdev->flags & IFF_UP))) {
 		kfree_skb(skb);
@@ -199,7 +200,12 @@ static int internal_dev_recv(struct sk_buff *skb)
 	nf_reset_ct(skb);
 
 	skb->pkt_type = PACKET_HOST;
-	skb->protocol = eth_type_trans(skb, netdev);
+	reason = eth_type_trans_careful(skb, netdev);
+	if (unlikely(reason)) {
+		dev_core_stats_rx_dropped_inc(netdev);
+		kfree_skb_reason(skb, reason);
+		return NETDEV_TX_OK;
+	}
 	skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
 	dev_sw_netstats_rx_add(netdev, skb->len);
 
-- 
2.53.0