tech@,

I had discovered one more crash which can be triggered by an application
when it sends ioctl(VIDIOC_STREAMOFF) into streaming isco webcam, or
when the device is detached.

To avoid such crash I'd like to add requirements that pipe is still
open, before parse header, or schedule a new isoc transfer.

Ok?

Index: sys/dev/usb/uvideo.c
===================================================================
RCS file: /home/cvs/src/sys/dev/usb/uvideo.c,v
diff -u -p -r1.251 uvideo.c
--- sys/dev/usb/uvideo.c	10 Mar 2025 07:38:12 -0000	1.251
+++ sys/dev/usb/uvideo.c	10 Mar 2025 22:01:42 -0000
@@ -2291,7 +2291,7 @@ uvideo_vs_start_isoc_ixfer(struct uvideo
 
 	DPRINTF(2, "%s: %s\n", DEVNAME(sc), __func__);
 
-	if (usbd_is_dying(sc->sc_udev))
+	if (usbd_is_dying(sc->sc_udev) || sc->sc_vs_cur->pipeh == NULL)
 		return;
 
 	for (i = 0; i < sc->sc_nframes; i++)
@@ -2321,6 +2321,9 @@ uvideo_vs_cb(struct usbd_xfer *xfer, voi
 	struct uvideo_softc *sc = ixfer->sc;
 	int len, i, frame_size;
 	uint8_t *frame, *buf;
+
+	if (usbd_is_dying(sc->sc_udev) || sc->sc_vs_cur->pipeh == NULL)
+		return;
 
 	DPRINTF(2, "%s: %s\n", DEVNAME(sc), __func__);