netdev - Re: [RFC PATCH v1] tun: Cleanup error handling in tun_set

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Date:	Sun, 09 Aug 2009 21:52:46 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ebiederm@...ssion.com
Cc:	herbert@...dor.apana.org.au, paul.moore@...com,
	netdev@...r.kernel.org
Subject: Re: [RFC PATCH v1] tun: Cleanup error handling in tun_set_iff()

From: ebiederm@...ssion.com (Eric W. Biederman)
Date: Thu, 06 Aug 2009 21:22:42 -0700

> David Miller <davem@...emloft.net> writes:
> 
>> From: Herbert Xu <herbert@...dor.apana.org.au>
>> Date: Fri, 7 Aug 2009 10:22:44 +1000
>>
>>> tun: Extend RTNL lock coverage over whole ioctl
>>> 
>>> As it is, parts of the ioctl runs under the RTNL and parts of
>>> it do not.  The unlocked section is still protected by the BKL,
>>> but there can be subtle races.  For example, Eric Biederman and
>>> Paul Moore observed that if two threads tried to create two tun
>>> devices on the same file descriptor, then unexpected results
>>> may occur.
>>> 
>>> As there isn't anything in the ioctl that is expected to sleep
>>> indefinitely, we can prevent this from occurring by extending
>>> the RTNL lock coverage.
>>> 
>>> This also allows to get rid of the BKL.
>>> 
>>> Finally, I changed tun_get_iff to take a tun device in order to
>>> avoid calling tun_put which would dead-lockt as it also tries to
>>> take the RTNL lock.
>>> 
>>> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
>>
>> This looks good after a quick audit, Eric what say you?
> 
> Looks good to me.

Applied, thanks everyone.
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