tree 4f838123d0b295ab3608380ce803c8960a8ebfd0
parent b9f9d4706cb1b706f89f98ea6ead41ebecdefbc2
author KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> 1257978386 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1258039556 -0800

memcg: fix wrong pointer initialization at page migration when memcg is disabled.

Lee Schermerhorn reported that he saw bad pointer dereference in
mem_cgroup_end_migration() when he disabled memcg by boot option.

memcg's page migration logic works as

	mem_cgroup_prepare_migration(page, &ptr);
	do page migration
	mem_cgroup_end_migration(page, ptr);

Now, ptr is not initialized in prepare_migration when memcg is disabled
by boot option. This causes panic in end_migration. This patch fixes it.

Reported-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>