From dabb047c62668f280998e29117c55e41aabac336 Mon Sep 17 00:00:00 2001 From: Valery Borovsky Date: Sat, 23 May 2026 19:53:37 +0300 Subject: [PATCH] media: rtl2832_sdr: use vb2_video_unregister_device() on remove to fix DMA leak 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: stable@vger.kernel.org Suggested-by: Hans Verkuil Signed-off-by: Valery Borovsky Signed-off-by: Hans Verkuil --- drivers/media/dvb-frontends/rtl2832_sdr.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 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); - mutex_lock(&dev->v4l2_lock); - /* No need to keep the urbs around after disconnection */ - dev->udev = NULL; + /* + * 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); - video_unregister_device(&dev->vdev); + vb2_video_unregister_device(&dev->vdev); + + mutex_lock(&dev->v4l2_lock); + dev->udev = NULL; mutex_unlock(&dev->v4l2_lock); - mutex_unlock(&dev->vb_queue_lock); + v4l2_device_put(&dev->v4l2_dev); module_put(pdev->dev.parent->driver->owner); }