[PATCH] mci: fix NULL pointer dereference

[Michael Tretter]

Calling `devlookup -k` directly on an mmc device instead of an partition
causes a NULL pointer dereference for cdevm.

Return a NULL pointer in this case to signal the error.

Signed-off-by: Michael Tretter <m.tret...@pengutronix.de>
---
 drivers/mci/mci-core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
index 592543faa7b8..abcda497646d 100644
--- a/drivers/mci/mci-core.c
+++ b/drivers/mci/mci-core.c
@@ -2536,6 +2536,9 @@ static char *mci_get_linux_mmcblkdev(struct block_device 
*blk,
        if (mci_part->area_type != MMC_BLK_DATA_AREA_MAIN)
                return NULL;
 
+       if (!cdevm)
+               return NULL;
+
        id = of_alias_get_id(cdev_of_node(cdevm), "mmc");
        if (id < 0)
                return NULL;
-- 
2.39.5