rtc: ab-b5ze-s3: fix possible race conditions

The IRQ is requested before the struct rtc is allocated and registered, but
this struct is used in the IRQ handler. This may lead to a NULL pointer
dereference.

Also, 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* */

Switch to devm_rtc_allocate_device/rtc_register_device to allocate the rtc
before requesting the IRQ and register the RTC as late as possible.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Alexandre Belloni 2018-05-17 22:20:39 +02:00
parent 02f3712f1f
commit 8bde032b28

View File

@ -925,6 +925,14 @@ static int abb5zes3_probe(struct i2c_client *client,
if (ret)
goto err;
data->rtc = devm_rtc_allocate_device(dev);
ret = PTR_ERR_OR_ZERO(data->rtc);
if (ret) {
dev_err(dev, "%s: unable to allocate RTC device (%d)\n",
__func__, ret);
goto err;
}
if (client->irq > 0) {
ret = devm_request_threaded_irq(dev, client->irq, NULL,
_abb5zes3_rtc_interrupt,
@ -942,14 +950,7 @@ static int abb5zes3_probe(struct i2c_client *client,
}
}
data->rtc = devm_rtc_device_register(dev, DRV_NAME, &rtc_ops,
THIS_MODULE);
ret = PTR_ERR_OR_ZERO(data->rtc);
if (ret) {
dev_err(dev, "%s: unable to register RTC device (%d)\n",
__func__, ret);
goto err;
}
data->rtc->ops = &rtc_ops;
/* Enable battery low detection interrupt if battery not already low */
if (!data->battery_low && data->irq) {
@ -961,6 +962,8 @@ static int abb5zes3_probe(struct i2c_client *client,
}
}
ret = rtc_register_device(data->rtc);
err:
if (ret && data && data->irq)
device_init_wakeup(dev, false);