linux-kernel - Re: [PATCH 1/1] net: bridge: fix a bug on using a neighbour cache entry without checking its state

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Date:   Mon, 07 Jan 2019 09:10:31 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     kchen@...ology.com
Cc:     nikolay@...ulusnetworks.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] net: bridge: fix a bug on using a neighbour cache
 entry without checking its state

From: kchen <kchen@...ology.com>
Date: Sun,  6 Jan 2019 11:28:13 +0800

> From: JianJhen Chen <kchen@...ology.com>
> 
> 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>

Indeed, this looks correct.

Applied and queued up for -stable, thanks.