media: pvrusb2: Fix oops on tear-down when radio support is not present

BugLink: https://bugs.launchpad.net/bugs/1858462

[ Upstream commit 7f404ae9 ]

In some device configurations there's no radio or radio support in the
driver.  That's OK, as the driver sets itself up accordingly.  However
on tear-down in these caes it's still trying to tear down radio
related context when there isn't anything there, leading to
dereferences through a null pointer and chaos follows.

How this bug survived unfixed for 11 years in the pvrusb2 driver is a
mystery to me.

[hverkuil: fix two checkpatch warnings]
Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/media/usb/pvrusb2/pvrusb2-v4l2.c

@@ -886,8 +886,12 @@ static void pvr2_v4l2_internal_check(struct pvr2_channel *chp)
 	pvr2_v4l2_dev_disassociate_parent(vp->dev_video);
 	pvr2_v4l2_dev_disassociate_parent(vp->dev_radio);
 	if (!list_empty(&vp->dev_video->devbase.fh_list) ||
-	    !list_empty(&vp->dev_radio->devbase.fh_list))
+	    (vp->dev_radio &&
+	     !list_empty(&vp->dev_radio->devbase.fh_list))) {
+		pvr2_trace(PVR2_TRACE_STRUCT,
+			   "pvr2_v4l2 internal_check exit-empty id=%p", vp);
 		return;
+	}
 	pvr2_v4l2_destroy_no_lock(vp);
 }
 
@@ -961,7 +965,8 @@ static int pvr2_v4l2_release(struct file *file)
 	kfree(fhp);
 	if (vp->channel.mc_head->disconnect_flag &&
 	    list_empty(&vp->dev_video->devbase.fh_list) &&
-	    list_empty(&vp->dev_radio->devbase.fh_list)) {
+	    (!vp->dev_radio ||
+	     list_empty(&vp->dev_radio->devbase.fh_list))) {
 		pvr2_v4l2_destroy_no_lock(vp);
 	}
 	return 0;