linux-kernel - [ 040/110] ip_tunnel: Fix a memory corruption in ip_tunnel

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Date:	Fri, 11 Oct 2013 12:38:20 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Pravin Shelar <pshelar@...ira.com>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 040/110] ip_tunnel: Fix a memory corruption in ip_tunnel_xmit

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

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

From: Steffen Klassert <steffen.klassert@...unet.com>

[ Upstream commit 3e08f4a72f689c6296d336c2aab4bddd60c93ae2 ]

We might extend the used aera of a skb beyond the total
headroom when we install the ipip header. Fix this by
calling skb_cow_head() unconditionally.

Bug was introduced with commit c544193214
("GRE: Refactor GRE tunneling code.")

Cc: Pravin Shelar <pshelar@...ira.com>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/ip_tunnel.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -659,13 +659,13 @@ void ip_tunnel_xmit(struct sk_buff *skb,
 
 	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr)
 					       + rt->dst.header_len;
-	if (max_headroom > dev->needed_headroom) {
+	if (max_headroom > dev->needed_headroom)
 		dev->needed_headroom = max_headroom;
-		if (skb_cow_head(skb, dev->needed_headroom)) {
-			dev->stats.tx_dropped++;
-			dev_kfree_skb(skb);
-			return;
-		}
+
+	if (skb_cow_head(skb, dev->needed_headroom)) {
+		dev->stats.tx_dropped++;
+		dev_kfree_skb(skb);
+		return;
 	}
 
 	skb_dst_drop(skb);


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