[PATCH] mmc: core: Fix null pointer dereference in bus_shutdown

[Seunghui Lee <sh043.lee@samsung.com>]

When shutting down removable device,
it can be occurred null pointer dereference.

To prevent null pointer dereference,
At first, check null pointer.
Next, block rescan worker to scan removable device during shutdown.

Signed-off-by: Seunghui Lee <sh043.lee@samsung.com>
---
 drivers/mmc/core/bus.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/core/bus.c b/drivers/mmc/core/bus.c
index 0af96548e7da..4f370a6577aa 100644
--- a/drivers/mmc/core/bus.c
+++ b/drivers/mmc/core/bus.c
@@ -143,9 +143,17 @@ static void mmc_bus_shutdown(struct device *dev)
 {
 	struct mmc_driver *drv = to_mmc_driver(dev->driver);
 	struct mmc_card *card = mmc_dev_to_card(dev);
-	struct mmc_host *host = card->host;
+	struct mmc_host *host;
 	int ret;
 
+	if (!drv || !card) {
+		pr_debug("%s: drv or card is NULL.\n", dev_name(dev));
+		return;
+	}
+
+	host = card->host;
+	host->rescan_disable = 1;
+
 	if (dev->driver && drv->shutdown)
 		drv->shutdown(card);
 
-- 
2.29.0