linux-kernel - Re: [PATCH] KVM: release anon file in failure path of vm creation

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Date:	Fri, 15 Jul 2016 11:18:41 +0800
From:	Liu Shuo <shuo.a.liu@...el.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	He Bo <bo.he@...el.com>, Liu Shuo <shuox.liu@...il.com>,
	Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH] KVM: release anon file in failure path of vm creation

On Fri 15.Jul'16 at  3:26:03 +0100, Al Viro wrote:
>On Fri, Jul 15, 2016 at 10:22:04AM +0800, Liu Shuo wrote:
>> > You have no warranty whatsoever that descriptor table has not been changed
>> > by that point.  You should *NEVER* use sys_close() on failure exit paths
>> Could you please elaborate why we're not sure descriptor table's changing at the point?
>
>Because that could be called by one thread while another (having guessed the
>descriptor you are about to get) does close()/dup2()/etc.
If there is no such thread (who operates the descriptor based on
guessing), i can think the changing is safe at the point. As the fd has
not been delivered to userspace. Am i right?