media: gscpa/stv06xx: fix memory leak

For two of the supported sensors the stv06xx driver allocates memory which
is stored in sd->sensor_priv. This memory is freed on a disconnect, but if
the probe() fails, then it isn't freed and so this leaks memory.

Add a new probe_error() op that drivers can use to free any allocated
memory in case there was a probe failure.

Thanks to Pavel Skripkin <paskripkin@gmail.com> for discovering the cause
of the memory leak.

Reported-and-tested-by: syzbot+e7f4c64a4248a0340c37@syzkaller.appspotmail.com
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/gspca/gspca.c

@@ -1576,6 +1576,8 @@ int gspca_dev_probe2(struct usb_interface *intf,
 #endif
 	v4l2_ctrl_handler_free(gspca_dev->vdev.ctrl_handler);
 	v4l2_device_unregister(&gspca_dev->v4l2_dev);
+	if (sd_desc->probe_error)
+		sd_desc->probe_error(gspca_dev);
 	kfree(gspca_dev->usb_buf);
 	kfree(gspca_dev);
 	return ret;

drivers/media/usb/gspca/gspca.h

@@ -105,6 +105,7 @@ struct sd_desc {
 	cam_cf_op config;	/* called on probe */
 	cam_op init;		/* called on probe and resume */
 	cam_op init_controls;	/* called on probe */
+	cam_v_op probe_error;	/* called if probe failed, do cleanup here */
 	cam_op start;		/* called on stream on after URBs creation */
 	cam_pkt_op pkt_scan;
 /* optional operations */

drivers/media/usb/gspca/stv06xx/stv06xx.c

@@ -529,12 +529,21 @@ static int sd_int_pkt_scan(struct gspca_dev *gspca_dev,
 static int stv06xx_config(struct gspca_dev *gspca_dev,
 			  const struct usb_device_id *id);
 
+static void stv06xx_probe_error(struct gspca_dev *gspca_dev)
+{
+	struct sd *sd = (struct sd *)gspca_dev;
+
+	kfree(sd->sensor_priv);
+	sd->sensor_priv = NULL;
+}
+
 /* sub-driver description */
 static const struct sd_desc sd_desc = {
 	.name = MODULE_NAME,
 	.config = stv06xx_config,
 	.init = stv06xx_init,
 	.init_controls = stv06xx_init_controls,
+	.probe_error = stv06xx_probe_error,
 	.start = stv06xx_start,
 	.stopN = stv06xx_stopN,
 	.pkt_scan = stv06xx_pkt_scan,