netdev - Re: [PATCH RFC net] neigh: do not modify unlinked entries

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Message-ID: <1434696010.31511.0.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 18 Jun 2015 23:40:10 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Julian Anastasov <ja@....bg>
Cc:	netdev@...r.kernel.org, Ying Xue <ying.xue@...driver.com>,
	alexei@...estorage.com, joern@...estorage.com
Subject: Re: [PATCH RFC net] neigh: do not modify unlinked entries

On Tue, 2015-06-16 at 22:56 +0300, Julian Anastasov wrote:
> The lockless lookups can return entry that is unlinked.
> Sometimes they get reference before last neigh_cleanup_and_release,
> sometimes they do not need reference. Later, any
> modification attempts may result in the following problems:
> 
> 1. entry is not destroyed immediately because neigh_update
> can start the timer for dead entry, eg. on change to NUD_REACHABLE
> state. As result, entry lives for some time but is invisible
> and out of control.
> 
> 2. __neigh_event_send can run in parallel with neigh_destroy
> while refcnt=0 but if timer is started and expired refcnt can
> reach 0 for second time leading to second neigh_destroy and
> possible crash.
> 
> Thanks to Eric Dumazet and Ying Xue for their work and analyze
> on the __neigh_event_send change.
> 
> Fixes: 767e97e1e0db ("neigh: RCU conversion of struct neighbour")
> Fixes: a263b3093641 ("ipv4: Make neigh lookups directly in output packet path.")
> Fixes: 6fd6ce2056de ("ipv6: Do not depend on rt->n in ip6_finish_output2().")
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Ying Xue <ying.xue@...driver.com>
> Signed-off-by: Julian Anastasov <ja@....bg>
> ---

Seems good to me Julian !

Acked-by: Eric Dumazet <edumazet@...gle.com>


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