[PATCH 3.18 11/68] net: neigh: guard against NULL solicit() method

Greg Kroah-Hartman
2017-05-05T18:56:46Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 48481c8fa16410ffa45939b13b6c53c2ca609e5f ]

Dmitry posted a nice reproducer of a bug triggering in neigh_probe()
when dereferencing a NULL neigh->ops->solicit method.

This can happen for arp_direct_ops/ndisc_direct_ops and similar,
which can be used for NUD_NOARP neighbours (created when dev->header_ops
is NULL). Admin can then force changing nud_state to some other state
that would fire neigh timer.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/core/neighbour.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -875,7 +875,8 @@ static void neigh_probe(struct neighbour
if (skb)
skb = skb_copy(skb, GFP_ATOMIC);
write_unlock(&neigh->lock);
- neigh->ops->solicit(neigh, skb);
+ if (neigh->ops->solicit)
+ neigh->ops->solicit(neigh, skb);
atomic_inc(&neigh->probes);
kfree_skb(skb);
}