linux-kernel - node-hotplug: is memset 0 safe in try_offline

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Date:	Tue, 3 Mar 2015 11:30:23 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tang Chen <tangchen@...fujitsu.com>,
	Yinghai Lu <yinghai@...nel.org>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	"Toshi Kani" <toshi.kani@...com>, Mel Gorman <mgorman@...e.de>,
	Tejun Heo <tj@...nel.org>
Subject: node-hotplug: is memset 0 safe in try_offline_node()?

When hot-remove a numa node, we will clear pgdat,
but is memset 0 safe in try_offline_node()?

process A:			offline node XX:
for_each_populated_zone()
find online node XX
cond_resched()
				offline cpu and memory, then try_offline_node()
				node_set_offline(nid), and memset(pgdat, 0, sizeof(*pgdat))
access node XX's pgdat
NULL pointer access error

Thanks,
Xishi Qiu

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