UBI: eliminate possible undefined behaviour

The assignment to pos when rb is finally NULL is undefined behaviour.
Upon seeing that assignment, GCC may assume that rb is not NULL, and
the loop condition ``rb'' may be optimised away.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 6a5fe9633783..c290f51dd178 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -579,7 +579,8 @@ void ubi_do_get_volume_info(struct ubi_device *ubi, struct ubi_volume *vol,
         for (rb = rb_first(root),                                            \
              pos = (rb ? container_of(rb, typeof(*pos), member) : NULL);     \
              rb;                                                             \
-             rb = rb_next(rb), pos = container_of(rb, typeof(*pos), member))
+             rb = rb_next(rb),                                               \
+             pos = (rb ? container_of(rb, typeof(*pos), member) : NULL))
 
 /**
  * ubi_zalloc_vid_hdr - allocate a volume identifier header object.