staging: rtl8712: fix race condition

In probe function, request_firmware_nowait() is called to load firmware
asynchronously. At completion of firmware loading, register_netdev() is
called. However, a mutex needed by netdev is initialized after the call
to request_firmware_nowait(). Consequently, it can happen that
register_netdev() is called before the driver is ready.

Move the mutex initialization into r8712_init_drv_sw(), which is called
before request_firmware_nowait().

Reported-by: syzbot+b08315e8cf5a78eed03c@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-staging/000000000000d9d4560601b8e0d7@google.com/T/#u
Fixes: 8c213fa591 ("staging: r8712u: Use asynchronous firmware loading")
Cc: stable <stable@kernel.org>
Signed-off-by: Nam Cao <namcaov@gmail.com>
Link: https://lore.kernel.org/r/20230731110620.116562-1-namcaov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/os_intfs.c

@@ -327,6 +327,7 @@ int r8712_init_drv_sw(struct _adapter *padapter)
 	mp871xinit(padapter);
 	init_default_value(padapter);
 	r8712_InitSwLeds(padapter);
+	mutex_init(&padapter->mutex_start);
 
 	return 0;
 

drivers/staging/rtl8712/usb_intf.c

@@ -567,7 +567,6 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
 	if (rtl871x_load_fw(padapter))
 		goto deinit_drv_sw;
 	init_completion(&padapter->rx_filter_ready);
-	mutex_init(&padapter->mutex_start);
 	return 0;
 
 deinit_drv_sw: