netdev - Re: [PATCH net] neighbor: Reset gc_entries counter if new entry is released before insert

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Date:   Sat, 04 May 2019 00:41:00 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     dsahern@...nel.org
Cc:     netdev@...r.kernel.org, ian.kumlien@...il.com,
        alan.maguire@...cle.com, dsahern@...il.com
Subject: Re: [PATCH net] neighbor: Reset gc_entries counter if new entry is
 released before insert

From: David Ahern <dsahern@...nel.org>
Date: Wed,  1 May 2019 18:08:34 -0700

> From: David Ahern <dsahern@...il.com>
> 
> Ian and Alan both reported seeing overflows after upgrades to 5.x kernels:
>   neighbour: arp_cache: neighbor table overflow!
> 
> Alan's mpls script helped get to the bottom of this bug. When a new entry
> is created the gc_entries counter is bumped in neigh_alloc to check if a
> new one is allowed to be created. ___neigh_create then searches for an
> existing entry before inserting the just allocated one. If an entry
> already exists, the new one is dropped in favor of the existing one. In
> this case the cleanup path needs to drop the gc_entries counter. There
> is no memory leak, only a counter leak.
> 
> Fixes: 58956317c8d ("neighbor: Improve garbage collection")
> Reported-by: Ian Kumlien <ian.kumlien@...il.com>
> Reported-by: Alan Maguire <alan.maguire@...cle.com>
> Signed-off-by: David Ahern <dsahern@...il.com>

Applied and queued up for -stable.