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: syzbot+5ca0bf339f13c4243001@syzkaller.appspotmail.com

Fixes: 85722118 ("[media] mxl111sf: convert to new DVB USB")
Signed-off-by: NPavel Skripkin <paskripkin@gmail.com>
Signed-off-by: NSean Young <sean@mess.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>

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

@@ -931,8 +931,6 @@ static int mxl111sf_init(struct dvb_usb_device *d)
 		  .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");
@@ -1074,6 +1072,14 @@ static int mxl111sf_get_stream_config_dvbt(struct dvb_frontend *fe,
 	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,
@@ -1083,6 +1089,7 @@ static struct dvb_usb_device_properties mxl111sf_props_dvbt = {
 	.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,
@@ -1124,6 +1131,7 @@ static struct dvb_usb_device_properties mxl111sf_props_atsc = {
 	.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,
@@ -1165,6 +1173,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mh = {
 	.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,
@@ -1233,6 +1242,7 @@ static struct dvb_usb_device_properties mxl111sf_props_atsc_mh = {
 	.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,
@@ -1311,6 +1321,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mercury = {
 	.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,
@@ -1381,6 +1392,7 @@ static struct dvb_usb_device_properties mxl111sf_props_mercury_mh = {
 	.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,