[PATCH 64/86] IP_GRE: Fix kernel panic in IP_GRE with GRE csum.

[Steven Rostedt]

3.6.11.1 stable review patch.
If anyone has any objections, please let me know.

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

From: Pravin B Shelar <pshelar@xxxxxxxxxx>

[ Upstream commit d0a7cc630a337b0f56dc145e7eb6232852b14dd4 ]

Due to IP_GRE GSO support, GRE can recieve non linear skb which
results in panic in case of GRE_CSUM.  Following patch fixes it by
using correct csum API.

Bug introduced in commit 6b78f16e4bdde3936b (gre: add GSO support)

Signed-off-by: Pravin B Shelar <pshelar@xxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
 net/ipv4/ip_gre.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index b062a98..3ee08ce 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -946,8 +946,12 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 			ptr--;
 		}
 		if (tunnel->parms.o_flags&GRE_CSUM) {
+			int offset = skb_transport_offset(skb);
+
 			*ptr = 0;
-			*(__sum16 *)ptr = ip_compute_csum((void *)(iph+1), skb->len - sizeof(struct iphdr));
+			*(__sum16 *)ptr = csum_fold(skb_checksum(skb, offset,
+								 skb->len - offset,
+								 0));
 		}
 	}
 
-- 
1.7.10.4


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