From a622260254ee481747cceaaa8609985b29a31565 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 24 May 2013 05:49:58 +0000 Subject: [PATCH] ip_tunnel: fix kernel panic with icmp_dest_unreach Daniel Petre reported crashes in icmp_dst_unreach() with following call graph: #3 [ffff88003fc03938] __stack_chk_fail at ffffffff81037f77 #4 [ffff88003fc03948] icmp_send at ffffffff814d5fec #5 [ffff88003fc03ae8] ipv4_link_failure at ffffffff814a1795 #6 [ffff88003fc03af8] ipgre_tunnel_xmit at ffffffff814e7965 #7 [ffff88003fc03b78] dev_hard_start_xmit at ffffffff8146e032 #8 [ffff88003fc03bc8] sch_direct_xmit at ffffffff81487d66 #9 [ffff88003fc03c08] __qdisc_run at ffffffff81487efd #10 [ffff88003fc03c48] dev_queue_xmit at ffffffff8146e5a7 #11 [ffff88003fc03c88] ip_finish_output at ffffffff814ab596 Daniel found a similar problem mentioned in http://lkml.indiana.edu/hypermail/linux/kernel/1007.0/00961.html And indeed this is the root cause : skb->cb[] contains data fooling IP stack. We must clear IPCB in ip_tunnel_xmit() sooner in case dst_link_failure() is called. Or else skb->cb[] might contain garbage from GSO segmentation layer. A similar fix was tested on linux-3.9, but gre code was refactored in linux-3.10. I'll send patches for stable kernels as well. Many thanks to Daniel for providing reports, patches and testing ! Reported-by: Daniel Petre Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/ip_tunnel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c index e4147ec1665a..be2f8da0ae8e 100644 --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -503,6 +503,7 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev, inner_iph = (const struct iphdr *)skb_inner_network_header(skb); + memset(IPCB(skb), 0, sizeof(*IPCB(skb))); dst = tnl_params->daddr; if (dst == 0) { /* NBMA tunnel */ @@ -658,7 +659,6 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev, skb_dst_drop(skb); skb_dst_set(skb, &rt->dst); - memset(IPCB(skb), 0, sizeof(*IPCB(skb))); /* Push down and install the IP header. */ skb_push(skb, sizeof(struct iphdr)); -- 2.39.2