[PATCH] media: airspy: Guard stop_streaming() against disconnected device

[Valery Borovsky <vebohr@gmail.com>]

airspy_disconnect() clears s->udev under v4l2_lock, but
airspy_stop_streaming() unconditionally calls airspy_ctrl_msg() and
airspy_free_stream_bufs() afterwards. If a streaming user closes the
device after disconnect, stop_streaming() runs and dereferences the
NULL s->udev:

  airspy_stop_streaming()
    airspy_ctrl_msg(s, CMD_RECEIVER_MODE, 0, 0, NULL, 0)
      usb_sndctrlpipe(s->udev, 0)         /* NULL deref */
    airspy_free_stream_bufs(s)
      usb_free_coherent(s->udev, ...)     /* NULL deref */

Mirror the precedent set by sibling SDR drivers msi2500 and pwc, which
already guard their hardware teardown block with an "if (udev)" check.
The queued-buffer drain via airspy_cleanup_queued_bufs() must still
run unconditionally so vb2 sees its buffers returned.

Issue identified by automated review of the INV-003 series at
https://sashiko.dev/

Fixes: 634fe5033951 ("[media] airspy: AirSpy SDR driver")
Cc: stable@vger.kernel.org
Signed-off-by: Valery Borovsky <vebohr@gmail.com>
---
 drivers/media/usb/airspy/airspy.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/media/usb/airspy/airspy.c b/drivers/media/usb/airspy/airspy.c
index 8f6b721ba107..50db02d35213 100644
--- a/drivers/media/usb/airspy/airspy.c
+++ b/drivers/media/usb/airspy/airspy.c
@@ -584,12 +584,14 @@ static void airspy_stop_streaming(struct vb2_queue *vq)
 
 	mutex_lock(&s->v4l2_lock);
 
-	/* stop hardware streaming */
-	airspy_ctrl_msg(s, CMD_RECEIVER_MODE, 0, 0, NULL, 0);
+	if (s->udev) {
+		/* stop hardware streaming */
+		airspy_ctrl_msg(s, CMD_RECEIVER_MODE, 0, 0, NULL, 0);
 
-	airspy_kill_urbs(s);
-	airspy_free_urbs(s);
-	airspy_free_stream_bufs(s);
+		airspy_kill_urbs(s);
+		airspy_free_urbs(s);
+		airspy_free_stream_bufs(s);
+	}
 
 	airspy_cleanup_queued_bufs(s);
 
-- 
2.51.0