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Subject[PATCH 2/2] mm: fix NULL ptr dereference in move_pages
Date
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@gmail.com>
---
mm/migrate.c | 16 ++++++++--------
1 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index 51c08a0..1107238 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -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 (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;
--
1.7.8.5


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