rtc: tps6586x: 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-tps6586x.c b/drivers/rtc/rtc-tps6586x.c
index 46a19adf9a96656c5d5ad1412e9673fd5606382e..9b741143f13121a767a35c8192217cbe07a18bd7 100644 (file)
--- a/drivers/rtc/rtc-tps6586x.c
+++ b/drivers/rtc/rtc-tps6586x.c
@@ -276,14 +276,15 @@ static int tps6586x_rtc_probe(struct platform_device *pdev)
        device_init_wakeup(&pdev->dev, 1);
 
        platform_set_drvdata(pdev, rtc);
-       rtc->rtc = devm_rtc_device_register(&pdev->dev, dev_name(&pdev->dev),
-                                      &tps6586x_rtc_ops, THIS_MODULE);
+       rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
        if (IS_ERR(rtc->rtc)) {
                ret = PTR_ERR(rtc->rtc);
-               dev_err(&pdev->dev, "RTC device register: ret %d\n", ret);
+               dev_err(&pdev->dev, "RTC allocate device: ret %d\n", ret);
                goto fail_rtc_register;
        }
 
+       rtc->rtc->ops = &tps6586x_rtc_ops;
+
        ret = devm_request_threaded_irq(&pdev->dev, rtc->irq, NULL,
                                tps6586x_rtc_irq,
                                IRQF_ONESHOT,
@@ -294,6 +295,13 @@ static int tps6586x_rtc_probe(struct platform_device *pdev)
                goto fail_rtc_register;
        }
        disable_irq(rtc->irq);
+
+       ret = rtc_register_device(rtc->rtc);
+       if (ret) {
+               dev_err(&pdev->dev, "RTC device register: ret %d\n", ret);
+               goto fail_rtc_register;
+       }
+
        return 0;
 
 fail_rtc_register: