linux-kernel - [034/205] net/core: neighbour update Oops

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Message-Id: <20100730175136.660204966@clark.site>
Date:	Fri, 30 Jul 2010 10:50:51 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Doug Kehn <rdkehn@...oo.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [034/205] net/core: neighbour update Oops

2.6.34-stable review patch.  If anyone has any objections, please let us know.

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

From: Doug Kehn <rdkehn@...oo.com>

commit 91a72a70594e5212c97705ca6a694bd307f7a26b upstream.

When configuring DMVPN (GRE + openNHRP) and a GRE remote
address is configured a kernel Oops is observed.  The
obserseved Oops is caused by a NULL header_ops pointer
(neigh->dev->header_ops) in neigh_update_hhs() when

void (*update)(struct hh_cache*, const struct net_device*, const unsigned char *)
= neigh->dev->header_ops->cache_update;

is executed.  The dev associated with the NULL header_ops is
the GRE interface.  This patch guards against the
possibility that header_ops is NULL.

This Oops was first observed in kernel version 2.6.26.8.

Signed-off-by: Doug Kehn <rdkehn@...oo.com>
Acked-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 net/core/neighbour.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -948,7 +948,10 @@ static void neigh_update_hhs(struct neig
 {
 	struct hh_cache *hh;
 	void (*update)(struct hh_cache*, const struct net_device*, const unsigned char *)
-		= neigh->dev->header_ops->cache_update;
+		= NULL;
+
+	if (neigh->dev->header_ops)
+		update = neigh->dev->header_ops->cache_update;

 	if (update) {
 		for (hh = neigh->hh; hh; hh = hh->hh_next) {

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