rtc: vr41xx: fix possible race condition

The probe function is not allowed to fail after the RTC is registered
because the following may happen:

CPU0:                                CPU1:
sys_load_module()
 do_init_module()
  do_one_initcall()
   cmos_do_probe()
    rtc_device_register()
     __register_chrdev()
     cdev->owner = struct module*
                                     open("/dev/rtc0")
    rtc_device_unregister()
  module_put()
  free_module()
   module_free(mod->module_core)
   /* struct module *module is now
      freed */
                                      chrdev_open()
                                       spin_lock(cdev_lock)
                                       cdev_get()
                                        try_module_get()
                                         module_is_live()
                                         /* dereferences already
                                            freed struct module* */

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

diff --git a/drivers/rtc/rtc-vr41xx.c b/drivers/rtc/rtc-vr41xx.c
index 480cffe8d3219dc863bb909ed079bd45d87f8472..2f1212a25f7e9b0ab3d64dc65db669035d137767 100644 (file)
--- a/drivers/rtc/rtc-vr41xx.c
+++ b/drivers/rtc/rtc-vr41xx.c
@@ -292,13 +292,14 @@ static int rtc_probe(struct platform_device *pdev)
                goto err_rtc1_iounmap;
        }
 
-       rtc = devm_rtc_device_register(&pdev->dev, rtc_name, &vr41xx_rtc_ops,
-                                       THIS_MODULE);
+       rtc = devm_rtc_allocate_device(&pdev->dev);
        if (IS_ERR(rtc)) {
                retval = PTR_ERR(rtc);
                goto err_iounmap_all;
        }
 
+       rtc->ops = &vr41xx_rtc_ops;
+
        rtc->max_user_freq = MAX_PERIODIC_RATE;
 
        spin_lock_irq(&rtc_lock);
@@ -340,6 +341,10 @@ static int rtc_probe(struct platform_device *pdev)
 
        dev_info(&pdev->dev, "Real Time Clock of NEC VR4100 series\n");
 
+       retval = rtc_register_device(rtc);
+       if (retval)
+               goto err_iounmap_all;
+
        return 0;
 
 err_iounmap_all: