netdev - Re: netlink: Kill bogus lock_sock in netlink

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Message-ID: <20150516123242.GA683@gondor.apana.org.au>
Date:	Sat, 16 May 2015 20:32:42 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...hat.com>
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

On Fri, May 15, 2015 at 01:02:19PM -0400, David Miller wrote:
>
> 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.

You're quite right.  I forgot about that case.

However, the code as is still buggy because it fails to reset
portid when our auto-allocated portid collides with somebody
else, resulting in a bogus bind failure.

I'll fix that up too in a new patch.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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