linux-kernel - [ 048/143] ip_tunnel: fix kernel panic with icmp_dest

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Date:	Mon, 12 May 2014 02:32:48 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>, Willy Tarreau <w@....eu>
Subject: [ 048/143] ip_tunnel: fix kernel panic with icmp_dest_unreach

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

[ 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@...-rds.ro>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Willy Tarreau <w@....eu>
---
 net/ipv4/ipip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 860b5c5..49aa1ad 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -408,6 +408,7 @@ 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) {
@@ -494,7 +495,6 @@ 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);
-- 
1.7.12.2.21.g234cd45.dirty



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