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net: neigh: guard against NULL solicit() method 

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>
This commit is contained in:
Eric Dumazet 2017-03-23 12:39:21 -07:00 committed by David S. Miller
parent f35ec35e5e
commit 48481c8fa1
1 changed files with 2 additions and 1 deletions
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3
net/core/neighbour.c
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@ -860,7 +860,8 @@ static void neigh_probe(struct neighbour *neigh)
if (skb)
skb = skb_clone(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);
}