linux-kernel - [098/200] rtc-cmos: do dev_set_drvdata() earlier in the initialization

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Message-Id: <20100701174254.703438805@clark.site>
Date:	Thu, 01 Jul 2010 10:43:08 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Dan Carpenter <error27@...il.com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Paul Gortmaker <p_gortmaker@...oo.com>,
	Malte Schroder <maltesch@....de>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Herton Ronaldo Krzesinski <herton@...driva.com.br>
Subject: [098/200] rtc-cmos: do dev_set_drvdata() earlier in the initialization

2.6.34-stable review patch.  If anyone has any objections, please let me know.

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

From: Dan Carpenter <error27@...il.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@...cle.com>
Signed-off-by: Dan Carpenter <error27@...il.com>
Tested-by: Randy Dunlap <randy.dunlap@...cle.com>
Cc: Alessandro Zummo <a.zummo@...ertech.it>
Cc: Paul Gortmaker <p_gortmaker@...oo.com>
Cc: Malte Schroder <maltesch@....de>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Herton Ronaldo Krzesinski <herton@...driva.com.br>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.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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