net: neigh: guard against NULL solicit() method
commit 48481c8fa16410ffa45939b13b6c53c2ca609e5f upstream. 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: Willy Tarreau <w@1wt.eu>
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@ -873,7 +873,8 @@ static void neigh_probe(struct neighbour *neigh)
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if (skb)
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skb = skb_copy(skb, GFP_ATOMIC);
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write_unlock(&neigh->lock);
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neigh->ops->solicit(neigh, skb);
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if (neigh->ops->solicit)
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neigh->ops->solicit(neigh, skb);
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atomic_inc(&neigh->probes);
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kfree_skb(skb);
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}
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