linux-kernel - [PATCH 05/11] rtc: m41t80: Initialize clientdata before registering device

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Date:	Fri,  6 May 2011 18:20:48 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Thomas Gleixner <tglx@...utronix.de>,
	rtc-linux@...glegroups.com
Subject: [PATCH 05/11] rtc: m41t80: Initialize clientdata before registering device

Commit f44f7f96a20 ("RTC: Initialize kernel state from RTC") uncovered
an issue in a number of RTC drivers, where the drivers call
rtc_device_register before initializing the clientdata.

This frequently results in null pointer dereferences when the
rtc_device_register immediately makes use of the rtc device, calling
rtc_read_alarm.

The solution is to ensure the clientdata is initialized prior to registering
the rtc device.

CC: Wolfram Sang <w.sang@...gutronix.de>
CC: Alessandro Zummo <a.zummo@...ertech.it>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: rtc-linux@...glegroups.com
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/rtc/rtc-m41t80.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index 69fe664..eda128f 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -783,6 +783,9 @@ static int m41t80_probe(struct i2c_client *client,
 		goto exit;
 	}
 
+	clientdata->features = id->driver_data;
+	i2c_set_clientdata(client, clientdata);
+
 	rtc = rtc_device_register(client->name, &client->dev,
 				  &m41t80_rtc_ops, THIS_MODULE);
 	if (IS_ERR(rtc)) {
@@ -792,8 +795,6 @@ static int m41t80_probe(struct i2c_client *client,
 	}
 
 	clientdata->rtc = rtc;
-	clientdata->features = id->driver_data;
-	i2c_set_clientdata(client, clientdata);
 
 	/* Make sure HT (Halt Update) bit is cleared */
 	rc = i2c_smbus_read_byte_data(client, M41T80_REG_ALARM_HOUR);
-- 
1.7.3.2.146.gca209

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