linux-kernel - Re: [PATCH v2] fork: fix oops after fork failure

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Message-ID: <20120823160411.GA19305@somewhere.redhat.com>
Date:	Thu, 23 Aug 2012 18:04:14 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH v2] fork: fix oops after fork failure

On Thu, Aug 23, 2012 at 07:36:08PM +0400, Glauber Costa wrote:
> When we want to duplicate a new process, dup_task_struct() will undergo
> a series of allocations. If alloc_thread_info_node() fails, we call
> free_task_struct() and return.
> 
> This seems right, but it is not. free_task_struct() will not only free
> the task struct from the kmem_cache, but will also call
> arch_release_task_struct(). The problem is that this function is
> supposed to undo whatever arch-specific work done by
> arch_dup_task_struct(), that is not yet called at this point.  The
> particular problem I ran accross was that in x86, we will arrive at
> fpu_free() without having ever allocated it.
> 
> Signed-off-by: Glauber Costa <glommer@...allels.com>
> Reported-by: Frederic Weisbecker <fweisbec@...hat.com>

Tested-by: Frederic Weisbecker <fweisbec@...hat.com>
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