net/core: neighbour update Oops

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@yahoo.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 6ba1c0eece03..a4e0a7482c2b 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -949,7 +949,10 @@ static void neigh_update_hhs(struct neighbour *neigh)
 {
         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) {