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

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Message-ID: <503984AB.6030802@parallels.com>
Date:	Sat, 25 Aug 2012 22:06:35 -0400
From:	Glauber Costa <glommer@...allels.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	<linux-kernel@...r.kernel.org>, <torvalds@...ux-foundation.org>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	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 08/24/2012 06:08 PM, Andrew Morton wrote:
> On Thu, 23 Aug 2012 19:36:08 +0400
> Glauber Costa <glommer@...allels.com> 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.
> 
> I think ths was already fixed by f19b9f74b7ea3b ("fork: fix error
> handling in dup_task()").  As you would have noticed if you were
> preparing patches against up-to-date kernel versions!
> 
I am basing all my patches against mmotm (actually, Michal's git copy of
it...)
I might have missed one spin, though. It happens
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