rtc: tps6586x: fix possible race condition
authorAlexandre Belloni <alexandre.belloni@bootlin.com>
Thu, 17 May 2018 20:48:17 +0000 (22:48 +0200)
committerAlexandre Belloni <alexandre.belloni@bootlin.com>
Thu, 17 May 2018 20:54:22 +0000 (22:54 +0200)
commit63d22063073b0ab46d1e06fe633fb5de8f5c58e1
treea5bafd332a3436b98e5ae892d1708f73065f836b
parent30d7891ae903d1e2903033a3df453d7533011076
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>
drivers/rtc/rtc-tps6586x.c