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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>
This commit is contained in:
Alexandre Belloni 2018-05-17 22:47:05 +02:00
parent 94389b28ba
commit 9a99247c9c
1 changed files with 7 additions and 2 deletions
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9
drivers/rtc/rtc-vr41xx.c
View File

@ -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: