[PATCH 2/2] zram: fix uninitialized ZRAM not releasing backing device

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

Setting backing device is done before ZRAM initialization.
If we set the backing device, then remove the ZRAM module without
initializing the device, the backing device reference will be leaked
and the device will be hold forever.

Fix this by always check and release the backing device when resetting
or removing ZRAM.

Fixes: 013bf95a83ec ("zram: add interface to specif backing device")
Reported-by: Desheng Wu <deshengwu@tencent.com>
Signed-off-by: Kairui Song <kasong@tencent.com>
Cc: stable@vger.kernel.org
---
 drivers/block/zram/zram_drv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index dd48df5b97c8..dfe9a994e437 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2335,6 +2335,9 @@ static void zram_reset_device(struct zram *zram)
 	zram->limit_pages = 0;
 
 	if (!init_done(zram)) {
+		/* Backing device could be set before ZRAM initialization. */
+		reset_bdev(zram);
+
 		up_write(&zram->init_lock);
 		return;
 	}
-- 
2.47.0