3.2.93-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Sasha Levin <levinsasha928@xxxxxxxxx>
commit 6e8b09eaf268bceac0c62e389b4bc0cb83dfb8e5 upstream.
Commit 3268c63 ("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@xxxxxxxxx>
Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
mm/migrate.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1412,14 +1412,14 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid,
mm = get_task_mm(task);
put_task_struct(task);
- if (mm) {
- 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;
+ 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);
mmput(mm);
return err;