From: Wei-Chun Chao <weichunc@xxxxxxxxxxxx> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== [ Upstream commit 5882a07c72093dc3a18e2d2b129fb200686bb6ee ] 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: [<ffffffff816ac412>] tcp_gso_segment+0x122/0x410 [<ffffffff816bc74c>] inet_gso_segment+0x13c/0x390 [<ffffffff8164b39b>] skb_mac_gso_segment+0x9b/0x170 [<ffffffff816b3658>] skb_udp_tunnel_segment+0xd8/0x390 [<ffffffff816b3c00>] udp4_ufo_fragment+0x120/0x140 [<ffffffff816bc74c>] inet_gso_segment+0x13c/0x390 [<ffffffff8109d742>] ? default_wake_function+0x12/0x20 [<ffffffff8164b39b>] skb_mac_gso_segment+0x9b/0x170 [<ffffffff8164b4d0>] __skb_gso_segment+0x60/0xc0 [<ffffffff8164b6b3>] dev_hard_start_xmit+0x183/0x550 [<ffffffff8166c91e>] sch_direct_xmit+0xfe/0x1d0 [<ffffffff8164bc94>] __dev_queue_xmit+0x214/0x4f0 [<ffffffff8164bf90>] dev_queue_xmit+0x10/0x20 [<ffffffff81687edb>] ip_finish_output+0x66b/0x890 [<ffffffff81688a58>] ip_output+0x58/0x90 [<ffffffff816c628f>] ? fib_table_lookup+0x29f/0x350 [<ffffffff816881c9>] ip_local_out_sk+0x39/0x50 [<ffffffff816cbfad>] iptunnel_xmit+0x10d/0x130 [<ffffffffa0212200>] vxlan_xmit_skb+0x1d0/0x330 [vxlan] [<ffffffffa02a3919>] vxlan_tnl_send+0x129/0x1a0 [openvswitch] [<ffffffffa02a2cd6>] ovs_vport_send+0x26/0xa0 [openvswitch] [<ffffffffa029931e>] do_output+0x2e/0x50 [openvswitch] Signed-off-by: Wei-Chun Chao <weichunc@xxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- 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 5a60953e6f39..aeb870c5c134 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2744,12 +2744,13 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, int i = 0; int pos; + __skb_push(head_skb, doffset); proto = skb_network_protocol(head_skb); 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); -- 2.0.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html