[PATCH] vivid: fix error handling of kthread_run

[Hans Verkuil]

kthread_run returns an error pointer, but elsewhere in the code 
dev->kthread_vid_cap/out
is checked against NULL.

If kthread_run returns an error, then set the pointer to NULL.

I chose this method over changing all kthread_vid_cap/out tests elsewhere since 
this
is more robust.

Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
Reported-by: syzbot+53d5b2df0d9744411...@syzkaller.appspotmail.com
---
diff --git a/drivers/media/platform/vivid/vivid-kthread-cap.c 
b/drivers/media/platform/vivid/vivid-kthread-cap.c
index f06003bb8e42..2a92e5aac9ed 100644
--- a/drivers/media/platform/vivid/vivid-kthread-cap.c
+++ b/drivers/media/platform/vivid/vivid-kthread-cap.c
@@ -865,8 +865,11 @@ int vivid_start_generating_vid_cap(struct vivid_dev *dev, 
bool *pstreaming)
                        "%s-vid-cap", dev->v4l2_dev.name);

        if (IS_ERR(dev->kthread_vid_cap)) {
+               int err = PTR_ERR(dev->kthread_vid_cap);
+
+               dev->kthread_vid_cap = NULL;
                v4l2_err(&dev->v4l2_dev, "kernel_thread() failed\n");
-               return PTR_ERR(dev->kthread_vid_cap);
+               return err;
        }
        *pstreaming = true;
        vivid_grab_controls(dev, true);
diff --git a/drivers/media/platform/vivid/vivid-kthread-out.c 
b/drivers/media/platform/vivid/vivid-kthread-out.c
index 9981e7548019..488590594150 100644
--- a/drivers/media/platform/vivid/vivid-kthread-out.c
+++ b/drivers/media/platform/vivid/vivid-kthread-out.c
@@ -236,8 +236,11 @@ int vivid_start_generating_vid_out(struct vivid_dev *dev, 
bool *pstreaming)
                        "%s-vid-out", dev->v4l2_dev.name);

        if (IS_ERR(dev->kthread_vid_out)) {
+               int err = PTR_ERR(dev->kthread_vid_out);
+
+               dev->kthread_vid_out = NULL;
                v4l2_err(&dev->v4l2_dev, "kernel_thread() failed\n");
-               return PTR_ERR(dev->kthread_vid_out);
+               return err;
        }
        *pstreaming = true;
        vivid_grab_controls(dev, true);