[PATCH 1/2] uio_hv_generic: Fix kernel NULL pointer dereference in hv_uio_rescind

[Naman Jain <namjain@linux.microsoft.com>]

From: Saurabh Sengar <ssengar@linux.microsoft.com>

For primary VMBus channels primary_channel pointer is always NULL. This
pointer is valid only for the secondry channels.

Fix NULL pointer dereference by retrieving the device_obj from the parent
in the absence of a valid primary_channel pointer.

Fixes: ca3cda6fcf1e ("uio_hv_generic: add rescind support")
Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
---
 drivers/uio/uio_hv_generic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index b45653752301..c99890c16d29 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -109,7 +109,8 @@ static void hv_uio_channel_cb(void *context)
  */
 static void hv_uio_rescind(struct vmbus_channel *channel)
 {
-	struct hv_device *hv_dev = channel->primary_channel->device_obj;
+	struct hv_device *hv_dev = channel->primary_channel ?
+				   channel->primary_channel->device_obj : channel->device_obj;
 	struct hv_uio_private_data *pdata = hv_get_drvdata(hv_dev);
 
 	/*
-- 
2.34.1