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

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commit e00e431612c3a6e437a01f2129fd3843da0c982a upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
KAMEZAWA Hiroyuki
2009-11-11 14:26:26 -08:00
committed by Greg Kroah-Hartman
parent bd7d235146
commit 0c98d0c6dc
1 changed files with 1 additions and 1 deletions
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2
mm/migrate.c
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@@ -597,7 +597,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
struct page *newpage = get_new_page(page, private, &result);
int rcu_locked = 0;
int charge = 0;
struct mem_cgroup *mem;
struct mem_cgroup *mem = NULL;
if (!newpage)
return -ENOMEM;