[PATCH] block: sunvdc: add check for mdesc_grab()

[Liang He <windhl@xxxxxxx>]

In vdc_port_probe(), we should check the return value
of mdesc_grab() as it may return NULL, which can cause
potential NPD bug.

Fixes: 43fdf27470b2 ("[SPARC64]: Abstract out mdesc accesses for better MD update handling.")
Signed-off-by: Liang He <windhl@xxxxxxx>
---
 drivers/block/sunvdc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/block/sunvdc.c b/drivers/block/sunvdc.c
index fb855da971ee..d24a78199cdb 100644
--- a/drivers/block/sunvdc.c
+++ b/drivers/block/sunvdc.c
@@ -973,6 +973,9 @@ static int vdc_port_probe(struct vio_dev *vdev, const struct vio_device_id *id)
 
 	hp = mdesc_grab();
 
+	if (!hp)
+		return -ENODEV;
+
 	err = -ENODEV;
 	if ((vdev->dev_no << PARTITION_SHIFT) & ~(u64)MINORMASK) {
 		printk(KERN_ERR PFX "Port id [%llu] too large.\n",
-- 
2.25.1