From: xeb@mail.ru <xeb@mail.ru>
Date: Fri, 22 Jul 2011 20:49:40 +0000 (+0000)
Subject: gre: fix improper error handling
X-Git-Tag: v3.0.2~31
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=06e67267adf0e3b9a25a78250a1c7caefd36f843;p=karo-tx-linux.git

gre: fix improper error handling

[ Upstream commit 559fafb94ad9e4cd8774f39241917c57396f9fc5 ]

Fix improper protocol err_handler, current implementation is fully
unapplicable and may cause kernel crash due to double kfree_skb.

Signed-off-by: Dmitry Kozlov <xeb@mail.ru>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
index c6933f2ea310..3e3f75d96be5 100644
--- a/net/ipv4/gre.c
+++ b/net/ipv4/gre.c
@@ -15,6 +15,7 @@
 #include <linux/kmod.h>
 #include <linux/skbuff.h>
 #include <linux/in.h>
+#include <linux/ip.h>
 #include <linux/netdevice.h>
 #include <linux/version.h>
 #include <linux/spinlock.h>
@@ -97,27 +98,17 @@ drop:
 static void gre_err(struct sk_buff *skb, u32 info)
 {
 	const struct gre_protocol *proto;
-	u8 ver;
-
-	if (!pskb_may_pull(skb, 12))
-		goto drop;
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
+	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
 
-	ver = skb->data[1]&0x7f;
 	if (ver >= GREPROTO_MAX)
-		goto drop;
+		return;
 
 	rcu_read_lock();
 	proto = rcu_dereference(gre_proto[ver]);
-	if (!proto || !proto->err_handler)
-		goto drop_unlock;
-	proto->err_handler(skb, info);
-	rcu_read_unlock();
-	return;
-
-drop_unlock:
+	if (proto && proto->err_handler)
+		proto->err_handler(skb, info);
 	rcu_read_unlock();
-drop:
-	kfree_skb(skb);
 }
 
 static const struct net_protocol net_gre_protocol = {