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rtc: rp5c01: 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 2018-02-12 23:47:49 +01:00
parent 87c78d9512
commit bcdd559268
1 changed files with 10 additions and 2 deletions
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12
drivers/rtc/rtc-rp5c01.c
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@ -249,16 +249,24 @@ static int __init rp5c01_rtc_probe(struct platform_device *dev)
platform_set_drvdata(dev, priv);
rtc = devm_rtc_device_register(&dev->dev, "rtc-rp5c01", &rp5c01_rtc_ops,
THIS_MODULE);
rtc = devm_rtc_allocate_device(&dev->dev);
if (IS_ERR(rtc))
return PTR_ERR(rtc);
rtc->ops = &rp5c01_rtc_ops;
priv->rtc = rtc;
error = sysfs_create_bin_file(&dev->dev.kobj, &priv->nvram_attr);
if (error)
return error;
error = rtc_register_device(rtc);
if (error) {
sysfs_remove_bin_file(&dev->dev.kobj, &priv->nvram_attr);
return error;
}
return 0;
}