linux-kernel - [ 017/105] net: Fix skb_under_panic oops in neigh_resolve

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Message-Id: <20121028231542.256308645@decadent.org.uk>
Date:	Sun, 28 Oct 2012 23:15:53 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	"ramesh.nagappa@...il.com" <ramesh.nagappa@...il.com>,
	Ramesh Nagappa <ramesh.nagappa@...csson.com>,
	Shawn Lu <shawn.lu@...csson.com>,
	Robert Coulson <robert.coulson@...csson.com>,
	Billie Alsup <billie.alsup@...csson.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 017/105] net: Fix skb_under_panic oops in neigh_resolve_output

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

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

From: "ramesh.nagappa@...il.com" <ramesh.nagappa@...il.com>

[ Upstream commit e1f165032c8bade3a6bdf546f8faf61fda4dd01c ]

The retry loop in neigh_resolve_output() and neigh_connected_output()
call dev_hard_header() with out reseting the skb to network_header.
This causes the retry to fail with skb_under_panic. The fix is to
reset the network_header within the retry loop.

Signed-off-by: Ramesh Nagappa <ramesh.nagappa@...csson.com>
Reviewed-by: Shawn Lu <shawn.lu@...csson.com>
Reviewed-by: Robert Coulson <robert.coulson@...csson.com>
Reviewed-by: Billie Alsup <billie.alsup@...csson.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/core/neighbour.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 7aafaed..5b9709f 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1254,8 +1254,6 @@ int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb)
 	if (!dst)
 		goto discard;
 
-	__skb_pull(skb, skb_network_offset(skb));
-
 	if (!neigh_event_send(neigh, skb)) {
 		int err;
 		struct net_device *dev = neigh->dev;
@@ -1265,6 +1263,7 @@ int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb)
 			neigh_hh_init(neigh, dst);
 
 		do {
+			__skb_pull(skb, skb_network_offset(skb));
 			seq = read_seqbegin(&neigh->ha_lock);
 			err = dev_hard_header(skb, dev, ntohs(skb->protocol),
 					      neigh->ha, NULL, skb->len);
@@ -1295,9 +1294,8 @@ int neigh_connected_output(struct neighbour *neigh, struct sk_buff *skb)
 	unsigned int seq;
 	int err;
 
-	__skb_pull(skb, skb_network_offset(skb));
-
 	do {
+		__skb_pull(skb, skb_network_offset(skb));
 		seq = read_seqbegin(&neigh->ha_lock);
 		err = dev_hard_header(skb, dev, ntohs(skb->protocol),
 				      neigh->ha, NULL, skb->len);


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