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From: Greg KH on 1 Jul 2010 17:50
2.6.34-stable review patch. If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <error27(a)gmail.com>

commit 6ba8bcd457d9fc793ac9435aa2e4138f571d4ec5 upstream.

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

---
drivers/rtc/rtc-cmos.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -719,6 +719,9 @@ cmos_do_probe(struct device *dev, struct
}
}

+ 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
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);


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