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

[kchen]

From: David Miller <da...@davemloft.net>
Date: Mon, 07 Jan 2019 09:10:31 -0800

> From: David Miller <da...@davemloft.net>
>

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

From: JianJhen Chen <kc...@synology.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 <kc...@synology.com>
Reviewed-by: JinLin Chen <jlc...@synology.com>

Indeed, this looks correct.

Applied and queued up for -stable, thanks.

Thank you for the confirmation.