netdev - Re: [PATCH net] tcp/dccp: fix another race at listener dismantle

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Message-Id: <20160218.113651.1088682629104635773.davem@davemloft.net>
Date:	Thu, 18 Feb 2016 11:36:51 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	edumazet@...gle.com
Cc:	netdev@...r.kernel.org, idryomov@...il.com, eric.dumazet@...il.com
Subject: Re: [PATCH net] tcp/dccp: fix another race at listener dismantle

From: Eric Dumazet <edumazet@...gle.com>
Date: Thu, 18 Feb 2016 05:39:18 -0800

> Ilya reported following lockdep splat:
 ...
> To properly fix this issue, inet_csk_reqsk_queue_add() needs
> to return to its callers if the child as been queued
> into accept queue.
> 
> We also need to make sure listener is still there before
> calling sk->sk_data_ready(), by holding a reference on it,
> since the reference carried by the child can disappear as
> soon as the child is put on accept queue.
> 
> Reported-by: Ilya Dryomov <idryomov@...il.com>
> Fixes: ebb516af60e1 ("tcp/dccp: fix race at listener dismantle phase")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable.

Although if I were writing this myself I would probably make
inet_csk_reqsk_queue_add() return bool since the pointer isn't
used in any way other than as a NULL vs. non-NULL test.