[PATCH] mtd: core: check partition before dereference

[Tetsuo Handa]

syzbot is reporting NULL pointer dereference at mtd_check_of_node() [1],
for mtdram test device (CONFIG_MTD_MTDRAM) is not partition.

Link: https://syzkaller.appspot.com/bug?extid=fe013f55a2814a9e8cfd [1]
Reported-by: syzbot <syzbot+fe013f55a2814a9e8cfd at syzkaller.appspotmail.com>
Reported-by: kernel test robot <oliver.sang at intel.com>
Fixes: ad9b10d1eaada169 ("mtd: core: introduce of support for dynamic partitions")
Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
---
 drivers/mtd/mtdcore.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 6fafea80fd98..a9b8be9f40dc 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -559,6 +559,8 @@ static void mtd_check_of_node(struct mtd_info *mtd)
 		return;
 
 	/* Check if a partitions node exist */
+	if (!mtd_is_partition(mtd))
+		return;
 	parent = mtd->parent;
 	parent_dn = dev_of_node(&parent->dev);
 	if (!parent_dn)
-- 
2.34.1