netdev - Re: netlink: Kill bogus lock_sock in netlink

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Message-Id: <20150515.130219.331336809636676892.davem@redhat.com>
Date:	Fri, 15 May 2015 13:02:19 -0400 (EDT)
From:	David Miller <davem@...hat.com>
To:	herbert@...dor.apana.org.au
Cc:	eric.dumazet@...il.com, tgraf@...g.ch, netdev@...r.kernel.org,
	ying.xue@...driver.com
Subject: Re: netlink: Kill bogus lock_sock in netlink_insert

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Thu, 14 May 2015 14:02:30 +0800

> The commit c5adde9468b0714a051eac7f9666f23eb10b61f7 ("netlink:
> eliminate nl_sk_hash_lock") added a lock_sock to netlink_insert
> with no justifications whatsoever.
> 
> This patch kills it.
> 
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

Actually, Herbert, I think this lock_sock() is needed.

Otherwise nothing protects nlk_sk(sk)->portid, upon which we
perform a non-atomic test-and-set operation here.

If you remove the lock_sock(), two parallel bind/inserts are
possible on the same socket, potentially resulting in socket
state corruption.
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