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rtc: rk808: fix possible race condition

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The probe function is not allowed to fail after registering the RTC 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* */

Switch to devm_rtc_allocate_device/rtc_register_device to register the rtc
as late as possible.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Alexandre Belloni 2018-02-21 11:57:05 +01:00
parent 4cda172bc3
commit 201fac95e7
1 changed files with 7 additions and 7 deletions
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14
drivers/rtc/rtc-rk808.c
View file

@ -405,12 +405,11 @@ static int rk808_rtc_probe(struct platform_device *pdev)
device_init_wakeup(&pdev->dev, 1);
rk808_rtc->rtc = devm_rtc_device_register(&pdev->dev, "rk808-rtc",
&rk808_rtc_ops, THIS_MODULE);
if (IS_ERR(rk808_rtc->rtc)) {
ret = PTR_ERR(rk808_rtc->rtc);
return ret;
}
rk808_rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(rk808_rtc->rtc))
return PTR_ERR(rk808_rtc->rtc);
rk808_rtc->rtc->ops = &rk808_rtc_ops;
rk808_rtc->irq = platform_get_irq(pdev, 0);
if (rk808_rtc->irq < 0) {
@ -427,9 +426,10 @@ static int rk808_rtc_probe(struct platform_device *pdev)
if (ret) {
dev_err(&pdev->dev, "Failed to request alarm IRQ %d: %d\n",
rk808_rtc->irq, ret);
return ret;
}
return ret;
return rtc_register_device(rk808_rtc->rtc);
}
static struct platform_driver rk808_rtc_driver = {