[ 3.8.y.z extended stable ] Patch "ip_tunnel: fix kernel panic with icmp_dest_unreach" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ip_tunnel: fix kernel panic with icmp_dest_unreach

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From c8bfd5332f4aa7e30320a6477cfb51a70612b270 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Fri, 24 May 2013 05:49:58 +0000
Subject: ip_tunnel: fix kernel panic with icmp_dest_unreach

[ Upstream commit a622260254ee481747cceaaa8609985b29a31565 ]

Daniel Petre reported crashes in icmp_dst_unreach() with following call
graph:

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 <daniel.petre at rcs-rds.ro>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/ipv4/ip_gre.c | 2 +-
 net/ipv4/ipip.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index a85062b..e0c1929 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -767,6 +767,7 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 		tiph = &tunnel->parms.iph;
 	}

+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 	if ((dst = tiph->daddr) == 0) {
 		/* NBMA tunnel */

@@ -912,7 +913,6 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 	skb_push(skb, gre_hlen);
 	skb_reset_network_header(skb);
 	skb_set_transport_header(skb, sizeof(*iph));
-	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
 			      IPSKB_REROUTED);
 	skb_dst_drop(skb);
diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 191fc24..b3fc09d 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -489,6 +489,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (tos & 1)
 		tos = old_iph->tos;

+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 	if (!dst) {
 		/* NBMA tunnel */
 		if ((rt = skb_rtable(skb)) == NULL) {
@@ -571,7 +572,6 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	skb->transport_header = skb->network_header;
 	skb_push(skb, sizeof(struct iphdr));
 	skb_reset_network_header(skb);
-	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
 			      IPSKB_REROUTED);
 	skb_dst_drop(skb);
--
1.8.1.2