linux-kernel - Re: [Bugfix] sched: fix possible invalid memory access caused by CPU hot-addition

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Message-ID: <53575360.3010702@linux.intel.com>
Date:	Wed, 23 Apr 2014 13:45:04 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [Bugfix] sched: fix possible invalid memory access caused by
 CPU hot-addition

On 2014/4/23 13:32, Peter Zijlstra wrote:
> On Wed, Apr 23, 2014 at 10:45:13AM +0800, Jiang Liu wrote:
>> Hi Peter,
>> 	It's not for memoryless node, but to solve a race window
>> in CPU hot-addition. The related CPU hot-addition flow is:
>> 1) Handle CPU hot-addition event
>> 1.a) gather platform specific information
>> 1.b) associate hot-added CPU with a node
>> 1.c) create CPU device
>> 2) User online hot-added CPUs through sysfs:
>> 2.a)	cpu_up()
>> 2.b)		->try_online_node()
>> 2.c)			->hotadd_new_pgdat()
>> 2.d)			->node_set_online()
>>
>> So between 1.b and 2.c, kmalloc_node(nid) may cause invalid
>> memory access without the node_online(nid) check.
> 
> Any why was all this not in the Changelog?
Sorry, will add above message into changelog.
Thanks!
Gerry
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