[PATCH 6.1 0376/1191] media: rtl2832_sdr: release URBs and stream buffers on start_streaming() failure

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Valery Borovsky <vebohr@gmail.com>

commit fe50cdaebf12cd32ff9a44d92bfd6fbc2300dbd4 upstream.

rtl2832_sdr_start_streaming() calls rtl2832_sdr_alloc_stream_bufs(),
rtl2832_sdr_alloc_urbs() and rtl2832_sdr_submit_urbs() in sequence and
shares a single err: label that only unlocks the mutex and returns.
When alloc_urbs() succeeds but submit_urbs() fails, or when alloc_urbs()
itself returns -ENOMEM after alloc_stream_bufs() has already succeeded,
the URBs and/or the coherent DMA stream buffers stay allocated while
streaming reports failure to vb2. Two latent defects follow on the next
VIDIOC_STREAMON:

1) rtl2832_sdr_alloc_stream_bufs() unconditionally resets dev->buf_num
   to 0 and overwrites dev->buf_list[]/dev->dma_addr[], permanently
   leaking the coherent DMA memory allocated by the previous attempt.

2) rtl2832_sdr_alloc_urbs() never resets dev->urbs_initialized and only
   increments it. After a second successful pass urbs_initialized can
   exceed MAX_BULK_BUFS, so the subsequent rtl2832_sdr_free_urbs() walks
   from urbs_initialized - 1 down to 0 and reads past the end of
   dev->urb_list[], passing garbage pointers to usb_free_urb().

Mirror the teardown that stop_streaming() already performs: on the error
path call rtl2832_sdr_free_urbs() and rtl2832_sdr_free_stream_bufs()
before unlocking. Both helpers are idempotent (free_urbs kills and zeros
urbs_initialized; free_stream_bufs is gated on URB_BUF and clears the
buf_num counter), so partial-failure paths and the no-allocation paths
remain safe.

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
Signed-off-by: Valery Borovsky <vebohr@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/media/dvb-frontends/rtl2832_sdr.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/media/dvb-frontends/rtl2832_sdr.c
+++ b/drivers/media/dvb-frontends/rtl2832_sdr.c
@@ -905,9 +905,12 @@ static int rtl2832_sdr_start_streaming(s
 		goto err;
 
 	mutex_unlock(&dev->v4l2_lock);
+
 	return 0;
 
 err:
+	rtl2832_sdr_free_urbs(dev);
+	rtl2832_sdr_free_stream_bufs(dev);
 	rtl2832_sdr_cleanup_queued_bufs(dev, VB2_BUF_STATE_QUEUED);
 	mutex_unlock(&dev->v4l2_lock);