rtc-cmos: do dev_set_drvdata() earlier in the initialization

The bug is an oops when dev_get_drvdata() returned null in
cmos_update_irq_enable().  The call tree looks like this:
  rtc_dev_ioctl()
    => rtc_update_irq_enable()
      => cmos_update_irq_enable()

It's caused by a race condition in the module initialization.  It is
rtc_device_register() which makes the ioctl operations live so I moved
the call to dev_set_drvdata() before the call to rtc_device_register().

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=15963

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Dan Carpenter <error27@gmail.com>
Tested-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: Malte Schroder <maltesch@gmx.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 96e8e70fbf1e..11b8ea29d2b7 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -719,6 +719,9 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
                 }
         }
 
+        cmos_rtc.dev = dev;
+        dev_set_drvdata(dev, &cmos_rtc);
+
         cmos_rtc.rtc = rtc_device_register(driver_name, dev,
                                 &cmos_rtc_ops, THIS_MODULE);
         if (IS_ERR(cmos_rtc.rtc)) {
@@ -726,8 +729,6 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
                 goto cleanup0;
         }
 
-        cmos_rtc.dev = dev;
-        dev_set_drvdata(dev, &cmos_rtc);
         rename_region(ports, dev_name(&cmos_rtc.rtc->dev));
 
         spin_lock_irq(&rtc_lock);