Commit 6e8b09ea authored Apr 25, 2012 by Sasha Levin Committed by Linus Torvalds Apr 25, 2012

mm: fix NULL ptr dereference in move_pages



Commit 3268c63e ("mm: fix move/migrate_pages() race on task struct") has
added an odd construct where 'mm' is checked for being NULL, and if it is,
it would get dereferenced anyways by mput()ing it.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f2a9ef88

mm/migrate.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -1388,14 +1388,14 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
		mm = get_task_mm(task);
		put_task_struct(task);

		if (mm) {
		if (!mm)
		return -EINVAL;

		if (nodes)
		err = do_pages_move(mm, task_nodes, nr_pages, pages,
		nodes, status, flags);
		else
		err = do_pages_stat(mm, nr_pages, pages, status);
		} else
		err = -EINVAL;

		mmput(mm);
		return err;

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