[PATCH v1 1/2] Input: sur40 - don't wait for buffers nothing will complete

[PATCH v1 1/2] Input: sur40 - don't wait for buffers nothing will complete

[Nguyen Ngoc Thang]

sur40_stop_streaming() calls vb2_wait_for_all_buffers() before handing
the queued buffers back. Those buffers are only completed from the input
poll callback, which is gone once the device is unplugged. Closing a
video node that is still streaming after a disconnect then sleeps
forever in vb2_wait_for_all_buffers():

  vb2_wait_for_all_buffers+0x20f/0x330
  sur40_stop_streaming+0x45/0x310
  __vb2_queue_cancel+0xc5/0xf70
  vb2_core_streamoff+0x5d/0x180
  __vb2_cleanup_fileio+0x6e/0x190
  vb2_core_queue_release+0x1f/0x190
  _vb2_fop_release+0xe8/0x280
  v4l2_release+0x280/0x430

It has not been noticed so far because sur40_disconnect() frees the
device state under the open file, and the close then crashes earlier.

Return the queued buffers first. A buffer that sur40_process_video()
has already taken off the list still completes by itself, so the wait
afterwards only covers that one.

Fixes: 6a8588156657 ("[media] sur40: fix occasional oopses on device close")
Cc: stable@vger.kernel.org
Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>
---
 drivers/input/touchscreen/sur40.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/input/touchscreen/sur40.c b/drivers/input/touchscreen/sur40.c
index 09d8c5f8d09f..7020bcf9b81a 100644
--- a/drivers/input/touchscreen/sur40.c
+++ b/drivers/input/touchscreen/sur40.c
@@ -929,11 +929,11 @@ static int sur40_start_streaming(struct vb2_queue *vq, unsigned int count)
 static void sur40_stop_streaming(struct vb2_queue *vq)
 {
 	struct sur40_state *sur40 = vb2_get_drv_priv(vq);
-	vb2_wait_for_all_buffers(vq);
-	sur40->sequence = -1;
 
-	/* Release all active buffers */
+	/* Release queued buffers first: nothing completes them after unplug */
 	return_all_buffers(sur40, VB2_BUF_STATE_ERROR);
+	vb2_wait_for_all_buffers(vq);
+	sur40->sequence = -1;
 }
 
 /* V4L ioctl */
-- 
2.43.0

Re: [PATCH v1 1/2] Input: sur40 - don't wait for buffers nothing will complete

[Hans Verkuil]

On 20/09/2026 13:39, Nguyen Ngoc Thang wrote:
> sur40_stop_streaming() calls vb2_wait_for_all_buffers() before handing
> the queued buffers back. Those buffers are only completed from the input
> poll callback, which is gone once the device is unplugged. Closing a
> video node that is still streaming after a disconnect then sleeps
> forever in vb2_wait_for_all_buffers():
> 
>   vb2_wait_for_all_buffers+0x20f/0x330
>   sur40_stop_streaming+0x45/0x310
>   __vb2_queue_cancel+0xc5/0xf70
>   vb2_core_streamoff+0x5d/0x180
>   __vb2_cleanup_fileio+0x6e/0x190
>   vb2_core_queue_release+0x1f/0x190
>   _vb2_fop_release+0xe8/0x280
>   v4l2_release+0x280/0x430
> 
> It has not been noticed so far because sur40_disconnect() frees the
> device state under the open file, and the close then crashes earlier.
> 
> Return the queued buffers first. A buffer that sur40_process_video()
> has already taken off the list still completes by itself, so the wait
> afterwards only covers that one.
> 
> Fixes: 6a8588156657 ("[media] sur40: fix occasional oopses on device close")
> Cc: stable@vger.kernel.org
> Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>
> ---
>  drivers/input/touchscreen/sur40.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/sur40.c b/drivers/input/touchscreen/sur40.c
> index 09d8c5f8d09f..7020bcf9b81a 100644
> --- a/drivers/input/touchscreen/sur40.c
> +++ b/drivers/input/touchscreen/sur40.c
> @@ -929,11 +929,11 @@ static int sur40_start_streaming(struct vb2_queue *vq, unsigned int count)
>  static void sur40_stop_streaming(struct vb2_queue *vq)
>  {
>  	struct sur40_state *sur40 = vb2_get_drv_priv(vq);
> -	vb2_wait_for_all_buffers(vq);
> -	sur40->sequence = -1;
>  
> -	/* Release all active buffers */
> +	/* Release queued buffers first: nothing completes them after unplug */
>  	return_all_buffers(sur40, VB2_BUF_STATE_ERROR);
> +	vb2_wait_for_all_buffers(vq);
> +	sur40->sequence = -1;
>  }
>  
>  /* V4L ioctl */

I think you should make one more change: replace the video_unregister_device calls by
vb2_video_unregister_device(). This ensures that at unregister time all streaming is
canceled and stop_streaming is called.

Having streaming continue after unregistering a device is in general not a good idea,
which is why we added that vb2_video_unregister_device call.

I think you still need to have that change in stop_streaming for this specific driver,
but it might be worth testing without it.

Regards,

	Hans

[PATCH v1 2/2] Input: sur40 - keep device state alive until the video node is released

[Nguyen Ngoc Thang]

sur40_disconnect() frees the sur40_state, which embeds the video_device,
the v4l2_device and the vb2_queue, while a video node may still be open.
Closing that file afterwards touches freed memory:

  BUG: KASAN: slab-use-after-free in vb2_core_queue_release+0x12d/0x150
  Read of size 4 at addr ffff888066fa8aa8 by task v4l_id/28733
   vb2_core_queue_release+0x12d/0x150
   vb2_fop_release+0x16e/0x200
   v4l2_release+0x22c/0x350
   __fput+0x418/0xa50
  Freed by task 16811:
   kfree+0x1c5/0x650
   sur40_disconnect+0xaf/0x140

Give the v4l2_device a release callback that frees the bulk buffer and
the state, and drop the disconnect path's own reference with
v4l2_device_put(). The last closer of the node then does the freeing.
The probe error paths never open the node and keep freeing directly.

Reported-by: syzbot+eb4706daf505f9c4b547@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=eb4706daf505f9c4b547
Fixes: e831cd251fb9 ("[media] add raw video stream support for Samsung SUR40")
Cc: stable@vger.kernel.org
Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>
---
 drivers/input/touchscreen/sur40.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/input/touchscreen/sur40.c b/drivers/input/touchscreen/sur40.c
index 7020bcf9b81a..efd4fe557cef 100644
--- a/drivers/input/touchscreen/sur40.c
+++ b/drivers/input/touchscreen/sur40.c
@@ -648,6 +648,15 @@ static int sur40_input_setup_events(struct input_dev *input_dev)
 }
 
 /* Check candidate USB interface. */
+/* Runs once the last video node reference is gone. */
+static void sur40_release(struct v4l2_device *v4l2)
+{
+	struct sur40_state *sur40 = container_of(v4l2, struct sur40_state, v4l2);
+
+	kfree(sur40->bulk_in_buffer);
+	kfree(sur40);
+}
+
 static int sur40_probe(struct usb_interface *interface,
 		       const struct usb_device_id *id)
 {
@@ -733,6 +742,7 @@ static int sur40_probe(struct usb_interface *interface,
 			"Unable to register video master device.");
 		goto err_free_buffer;
 	}
+	sur40->v4l2.release = sur40_release;
 
 	/* initialize the lock and subdevice */
 	sur40->queue = sur40_queue;
@@ -831,11 +841,10 @@ static void sur40_disconnect(struct usb_interface *interface)
 	video_unregister_device(&sur40->vdev);
 	v4l2_device_unregister(&sur40->v4l2);
 
-	kfree(sur40->bulk_in_buffer);
-	kfree(sur40);
-
 	usb_set_intfdata(interface, NULL);
 	dev_dbg(&interface->dev, "%s is now disconnected\n", DRIVER_DESC);
+
+	v4l2_device_put(&sur40->v4l2);
 }
 
 /*
-- 
2.43.0

Re: [PATCH v1 2/2] Input: sur40 - keep device state alive until the video node is released

[Hans Verkuil]

On 20/09/2026 13:39, Nguyen Ngoc Thang wrote:
> sur40_disconnect() frees the sur40_state, which embeds the video_device,
> the v4l2_device and the vb2_queue, while a video node may still be open.
> Closing that file afterwards touches freed memory:
> 
>   BUG: KASAN: slab-use-after-free in vb2_core_queue_release+0x12d/0x150
>   Read of size 4 at addr ffff888066fa8aa8 by task v4l_id/28733
>    vb2_core_queue_release+0x12d/0x150
>    vb2_fop_release+0x16e/0x200
>    v4l2_release+0x22c/0x350
>    __fput+0x418/0xa50
>   Freed by task 16811:
>    kfree+0x1c5/0x650
>    sur40_disconnect+0xaf/0x140
> 
> Give the v4l2_device a release callback that frees the bulk buffer and
> the state, and drop the disconnect path's own reference with
> v4l2_device_put(). The last closer of the node then does the freeing.
> The probe error paths never open the node and keep freeing directly.
> 
> Reported-by: syzbot+eb4706daf505f9c4b547@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=eb4706daf505f9c4b547
> Fixes: e831cd251fb9 ("[media] add raw video stream support for Samsung SUR40")
> Cc: stable@vger.kernel.org
> Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>

Reviewed-by: Hans Verkuil <hverkuil+cisco@kernel.org>

Regards,

	Hans

> ---
>  drivers/input/touchscreen/sur40.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/sur40.c b/drivers/input/touchscreen/sur40.c
> index 7020bcf9b81a..efd4fe557cef 100644
> --- a/drivers/input/touchscreen/sur40.c
> +++ b/drivers/input/touchscreen/sur40.c
> @@ -648,6 +648,15 @@ static int sur40_input_setup_events(struct input_dev *input_dev)
>  }
>  
>  /* Check candidate USB interface. */
> +/* Runs once the last video node reference is gone. */
> +static void sur40_release(struct v4l2_device *v4l2)
> +{
> +	struct sur40_state *sur40 = container_of(v4l2, struct sur40_state, v4l2);
> +
> +	kfree(sur40->bulk_in_buffer);
> +	kfree(sur40);
> +}
> +
>  static int sur40_probe(struct usb_interface *interface,
>  		       const struct usb_device_id *id)
>  {
> @@ -733,6 +742,7 @@ static int sur40_probe(struct usb_interface *interface,
>  			"Unable to register video master device.");
>  		goto err_free_buffer;
>  	}
> +	sur40->v4l2.release = sur40_release;
>  
>  	/* initialize the lock and subdevice */
>  	sur40->queue = sur40_queue;
> @@ -831,11 +841,10 @@ static void sur40_disconnect(struct usb_interface *interface)
>  	video_unregister_device(&sur40->vdev);
>  	v4l2_device_unregister(&sur40->v4l2);
>  
> -	kfree(sur40->bulk_in_buffer);
> -	kfree(sur40);
> -
>  	usb_set_intfdata(interface, NULL);
>  	dev_dbg(&interface->dev, "%s is now disconnected\n", DRIVER_DESC);
> +
> +	v4l2_device_put(&sur40->v4l2);
>  }
>  
>  /*