[PATCH v1] mtd: ubi: fix kref leak on -EBUSY return in ubi_detach_mtd_dev()

[Yuho Choi <dbgh9129@gmail.com>]

ubi_detach_mtd_dev() calls ubi_get_device() which increments both
ubi->ref_count and the device kref via get_device(). When the device
is busy and anyway==0, the function returns -EBUSY after releasing
ubi_devices_lock, but never calls put_device() to drop the kref
acquired by ubi_get_device(). This leaks the kref, preventing the
device from ever being freed.

Commit 7e84c961b2eb ("mtd: ubi: introduce pre-removal notification
for UBI volumes") moved put_device() to after ubi->is_dead = true
to pair it with the notify+nullify sequence, but inadvertently left
the early -EBUSY return without a matching put_device().

Add put_device(&ubi->dev) before returning -EBUSY to balance the
get_device() inside ubi_get_device().

Fixes: 7e84c961b2eb ("mtd: ubi: introduce pre-removal notification for UBI volumes")
Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
---
 drivers/mtd/ubi/build.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 674ad87809df0..d81f5e0395ac0 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -1106,6 +1106,7 @@ int ubi_detach_mtd_dev(int ubi_num, int anyway)
 	if (ubi->ref_count) {
 		if (!anyway) {
 			spin_unlock(&ubi_devices_lock);
+			put_device(&ubi->dev);
 			return -EBUSY;
 		}
 		/* This may only happen if there is a bug */
-- 
2.50.1 (Apple Git-155)