media: mxl111sf: change mutex_init() location

Syzbot reported, that mxl111sf_ctrl_msg() uses uninitialized
mutex. The problem was in wrong mutex_init() location.

Previous mutex_init(&state->msg_lock) call was in ->init() function, but
dvb_usbv2_init() has this order of calls:

dvb_usbv2_init()
dvb_usbv2_adapter_init()
dvb_usbv2_adapter_frontend_init()
props->frontend_attach()

props->init()

Since mxl111sf_* devices call mxl111sf_ctrl_msg() in ->frontend_attach()
internally we need to initialize state->msg_lock before
frontend_attach(). To achieve it, ->probe() call added to all mxl111sf_*
devices, which will simply initiaize mutex.

Reported-and-tested-by: [e-mail]

Fixes: 8572211842af ("[media] mxl111sf: convert to new DVB USB")
Signed-off-by: Pavel Skripkin <[e-mail]>
Signed-off-by: Sean Young <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/usb/dvb-usb-v2/mxl111sf.c

···
 		  .len = sizeof(eeprom), .buf = eeprom },
 	};
 
-	mutex_init(&state->msg_lock);
-
 	ret = get_chip_info(state);
 	if (mxl_fail(ret))
 		pr_err("failed to get chip info during probe");
···
 	return 0;
 }
 
+static int mxl111sf_probe(struct dvb_usb_device *dev)
+{
+	struct mxl111sf_state *state = d_to_priv(dev);
+
+	mutex_init(&state->msg_lock);
+	return 0;
+}
+
 static struct dvb_usb_device_properties mxl111sf_props_dvbt = {
 	.driver_name = KBUILD_MODNAME,
 	.owner = THIS_MODULE,
···
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_dvbt,
 	.tuner_attach      = mxl111sf_attach_tuner,
···
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_atsc,
 	.tuner_attach      = mxl111sf_attach_tuner,
···
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
···
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_atsc_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,
···
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mercury,
 	.tuner_attach      = mxl111sf_attach_tuner,
···
 	.generic_bulk_ctrl_endpoint = 0x02,
 	.generic_bulk_ctrl_endpoint_response = 0x81,
 
+	.probe             = mxl111sf_probe,
 	.i2c_algo          = &mxl111sf_i2c_algo,
 	.frontend_attach   = mxl111sf_frontend_attach_mercury_mh,
 	.tuner_attach      = mxl111sf_attach_tuner,