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Subject: media: pvrusb2: Fix oops on tear-down when radio support is not present
Author:  Mike Isely <is...@pobox.com>
Date:    Wed Nov 6 12:11:14 2019 +0100

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 <is...@pobox.com>
Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+sams...@kernel.org>

 drivers/media/usb/pvrusb2/pvrusb2-v4l2.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

---

diff --git a/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c 
b/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c
index a34717eba409..eaa08c7999d4 100644
--- a/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c
+++ b/drivers/media/usb/pvrusb2/pvrusb2-v4l2.c
@@ -898,8 +898,12 @@ 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);
 }
 
@@ -935,7 +939,8 @@ 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;

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