From 5882a07c72093dc3a18e2d2b129fb200686bb6ee Mon Sep 17 00:00:00 2001 From: Wei-Chun Chao Date: Sun, 8 Jun 2014 23:48:54 -0700 Subject: [PATCH] net: fix UDP tunnel GSO of frag_list GRO packets This patch fixes a kernel BUG_ON in skb_segment. It is hit when testing two VMs on openvswitch with one VM acting as VXLAN gateway. During VXLAN packet GSO, skb_segment is called with skb->data pointing to inner TCP payload. skb_segment calls skb_network_protocol to retrieve the inner protocol. skb_network_protocol actually expects skb->data to point to MAC and it calls pskb_may_pull with ETH_HLEN. This ends up pulling in ETH_HLEN data from header tail. As a result, pskb_trim logic is skipped and BUG_ON is hit later. Move skb_push in front of skb_network_protocol so that skb->data lines up properly. kernel BUG at net/core/skbuff.c:2999! Call Trace: [] tcp_gso_segment+0x122/0x410 [] inet_gso_segment+0x13c/0x390 [] skb_mac_gso_segment+0x9b/0x170 [] skb_udp_tunnel_segment+0xd8/0x390 [] udp4_ufo_fragment+0x120/0x140 [] inet_gso_segment+0x13c/0x390 [] ? default_wake_function+0x12/0x20 [] skb_mac_gso_segment+0x9b/0x170 [] __skb_gso_segment+0x60/0xc0 [] dev_hard_start_xmit+0x183/0x550 [] sch_direct_xmit+0xfe/0x1d0 [] __dev_queue_xmit+0x214/0x4f0 [] dev_queue_xmit+0x10/0x20 [] ip_finish_output+0x66b/0x890 [] ip_output+0x58/0x90 [] ? fib_table_lookup+0x29f/0x350 [] ip_local_out_sk+0x39/0x50 [] iptunnel_xmit+0x10d/0x130 [] vxlan_xmit_skb+0x1d0/0x330 [vxlan] [] vxlan_tnl_send+0x129/0x1a0 [openvswitch] [] ovs_vport_send+0x26/0xa0 [openvswitch] [] do_output+0x2e/0x50 [openvswitch] Signed-off-by: Wei-Chun Chao Signed-off-by: David S. Miller --- net/core/skbuff.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 8383b2b..9433047 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2881,12 +2881,13 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, int pos; int dummy; + __skb_push(head_skb, doffset); proto = skb_network_protocol(head_skb, &dummy); if (unlikely(!proto)) return ERR_PTR(-EINVAL); csum = !!can_checksum_protocol(features, proto); - __skb_push(head_skb, doffset); + headroom = skb_headroom(head_skb); pos = skb_headlen(head_skb); -- 2.7.4