linux-kernel - [PATCH] rtc: Fix possible null pointer dereference in rtc-mpc5121.c

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Date:	Tue, 24 Apr 2012 13:43:35 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] rtc: Fix possible null pointer dereference in rtc-mpc5121.c

Hey Thomas,
	This is against tip/timers/urgent for 3.4
thanks
-john

Mark Loard pointed out:
"For example, this beauty from rtc-mpc5121.c in the same update:
   ...
   rtc->rtc = rtc_device_register("mpc5200-rtc", &op->dev,
                                   &mpc5200_rtc_ops, THIS_MODULE);
   ...

   rtc->rtc->uie_unsupported = 1;    // <<<< Ooops NULL pointer >>>>

   if (IS_ERR(rtc->rtc)) {           // <<<< this needs to be earlier >>>>
           err = PTR_ERR(rtc->rtc);
           goto out_free_irq;
   }
   ..."
This patch moves setting the uie_unsupported flag to after
we validate the rtc->rtc pointer to resolve this.

CC: Thomas Gleixner <tglx@...utronix.de>
Reported by: Mark Lord <kernel@...savvy.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/rtc/rtc-mpc5121.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-mpc5121.c b/drivers/rtc/rtc-mpc5121.c
index 42f5f82..029e421 100644
--- a/drivers/rtc/rtc-mpc5121.c
+++ b/drivers/rtc/rtc-mpc5121.c
@@ -360,12 +360,11 @@ static int __devinit mpc5121_rtc_probe(struct platform_device *op)
 						&mpc5200_rtc_ops, THIS_MODULE);
 	}
 
-	rtc->rtc->uie_unsupported = 1;
-
 	if (IS_ERR(rtc->rtc)) {
 		err = PTR_ERR(rtc->rtc);
 		goto out_free_irq;
 	}
+	rtc->rtc->uie_unsupported = 1;
 
 	return 0;
 
-- 
1.7.3.2.146.gca209

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