ipv6: route: Fix return value of ip6_neigh_lookup() on neigh_create() error

sbrivio-rh · davem330 · commit 7adf3246092f · 2019-01-02T10:29:20.000-08:00
In ip6_neigh_lookup(), we must not return errors coming from neigh_create(): if creation of a neighbour entry fails, the lookup should return NULL, in the same way as it's done in __neigh_lookup(). Otherwise, callers legitimately checking for a non-NULL return value of the lookup function might dereference an invalid pointer. For instance, on neighbour table overflow, ndisc_router_discovery() crashes ndisc_update() by passing ERR_PTR(-ENOBUFS) as 'neigh' argument. Reported-by: Jianlin Shi <jishi@redhat.com> Fixes: f8a1b43 ("net/ipv6: Create a neigh_lookup for FIB entries") Signed-off-by: Stefano Brivio <sbrivio@redhat.com> Reviewed-by: David Ahern <dsahern@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
@@ -210,7 +210,9 @@ struct neighbour *ip6_neigh_lookup(const struct in6_addr *gw,
 	n = __ipv6_neigh_lookup(dev, daddr);
 	if (n)
 		return n;
-	return neigh_create(&nd_tbl, daddr, dev);
+
+	n = neigh_create(&nd_tbl, daddr, dev);
+	return IS_ERR(n) ? NULL : n;
 }
 
 static struct neighbour *ip6_dst_neigh_lookup(const struct dst_entry *dst,
