On Sat May 23 19:53:37 2026 +0300, Valery Borovsky wrote:
> rtl2832_sdr_remove() runs on USB disconnect and clears dev->udev to
> NULL before any pending streaming teardown has run. When user space
> later closes its file descriptor, vb2 calls rtl2832_sdr_stop_streaming()
> which in turn calls rtl2832_sdr_free_stream_bufs(). That helper releases
> each coherent buffer with:
>
> usb_free_coherent(dev->udev, dev->buf_size,
> dev->buf_list[dev->buf_num],
> dev->dma_addr[dev->buf_num]);
>
> usb_free_coherent() returns immediately when its dev argument is NULL,
> so every DMA stream buffer that was live at disconnect is silently
> leaked. The URBs allocated in rtl2832_sdr_alloc_urbs() outlive the
> device for the same reason.
>
> The rtl2832_sdr driver uses vb2_fop_release() in its file_operations,
> so replace video_unregister_device(&dev->vdev) with
> vb2_video_unregister_device(&dev->vdev) and move it before clearing
> dev->udev. vb2_video_unregister_device() releases the vb2 queue, which
> synchronously runs rtl2832_sdr_stop_streaming() if streaming is active,
> so URBs and coherent DMA stream buffers are freed while dev->udev is
> still valid.
>
> vb2_video_unregister_device() locks vdev->queue->lock (vb_queue_lock)
> internally, and stop_streaming() locks v4l2_lock, so the previous outer
> mutex_lock(&dev->vb_queue_lock) / mutex_lock(&dev->v4l2_lock) pair
> around the unregister sequence would self-deadlock and has been removed.
> A short v4l2_lock critical section around dev->udev = NULL remains so
> any ioctl path that still holds the file descriptor sees coherent state.
>
> Issue identified by automated review of the INV-003 series at
> https://sashiko.dev/
>
> Fixes: 771138920eaf ("[media] rtl2832_sdr: Realtek RTL2832 SDR driver module")
> Cc: [email protected]
> Suggested-by: Hans Verkuil <[email protected]>
> Signed-off-by: Valery Borovsky <[email protected]>
> Signed-off-by: Hans Verkuil <[email protected]>
Patch committed.
Thanks,
Hans Verkuil
drivers/media/dvb-frontends/rtl2832_sdr.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
---
diff --git a/drivers/media/dvb-frontends/rtl2832_sdr.c
b/drivers/media/dvb-frontends/rtl2832_sdr.c
index c564485e3bbb..c1f5f07c42a8 100644
--- a/drivers/media/dvb-frontends/rtl2832_sdr.c
+++ b/drivers/media/dvb-frontends/rtl2832_sdr.c
@@ -1477,14 +1477,22 @@ static void rtl2832_sdr_remove(struct platform_device
*pdev)
dev_dbg(&pdev->dev, "\n");
- mutex_lock(&dev->vb_queue_lock);
+ /*
+ * vb2_video_unregister_device() releases the vb2 queue, which
+ * triggers rtl2832_sdr_stop_streaming() if streaming is active.
+ * stop_streaming() uses dev->udev to free URBs and coherent DMA
+ * stream buffers via usb_free_coherent(), so it must run before
+ * dev->udev is cleared. vb2_video_unregister_device() locks
+ * vb_queue_lock internally and stop_streaming() locks v4l2_lock,
+ * so neither may be held by the caller.
+ */
+ v4l2_device_disconnect(&dev->v4l2_dev);
+ vb2_video_unregister_device(&dev->vdev);
+
mutex_lock(&dev->v4l2_lock);
- /* No need to keep the urbs around after disconnection */
dev->udev = NULL;
- v4l2_device_disconnect(&dev->v4l2_dev);
- video_unregister_device(&dev->vdev);
mutex_unlock(&dev->v4l2_lock);
- mutex_unlock(&dev->vb_queue_lock);
+
v4l2_device_put(&dev->v4l2_dev);
module_put(pdev->dev.parent->driver->owner);
}
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