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Date: Mon, 21 Jan 2019 14:44:10 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, JianJhen Chen <kchen@...ology.com>, JinLin Chen <jlchen@...ology.com>, "David S. Miller" <davem@...emloft.net> Subject: [PATCH 4.9 14/51] net: bridge: fix a bug on using a neighbour cache entry without checking its state 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: JianJhen Chen <kchen@...ology.com> [ Upstream commit 4c84edc11b76590859b1e45dd676074c59602dc4 ] When handling DNAT'ed packets on a bridge device, the neighbour cache entry from lookup was used without checking its state. It means that a cache entry in the NUD_STALE state will be used directly instead of entering the NUD_DELAY state to confirm the reachability of the neighbor. This problem becomes worse after commit 2724680bceee ("neigh: Keep neighbour cache entries if number of them is small enough."), since all neighbour cache entries in the NUD_STALE state will be kept in the neighbour table as long as the number of cache entries does not exceed the value specified in gc_thresh1. This commit validates the state of a neighbour cache entry before using the entry. Signed-off-by: JianJhen Chen <kchen@...ology.com> Reviewed-by: JinLin Chen <jlchen@...ology.com> Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- net/bridge/br_netfilter_hooks.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -275,7 +275,7 @@ int br_nf_pre_routing_finish_bridge(stru struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb); int ret; - if (neigh->hh.hh_len) { + if ((neigh->nud_state & NUD_CONNECTED) && neigh->hh.hh_len) { neigh_hh_bridge(&neigh->hh, skb); skb->dev = nf_bridge->physindev; ret = br_handle_frame_finish(net, sk, skb);
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