rtc: mxc: Initialize drvdata 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 device or platform drvdata.

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 drvdata is initialized prior to registering
the rtc device.

CC: Alessandro Zummo <a.zummo@towertech.it>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: rtc-linux@googlegroups.com
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
[fixed up commit log -jstultz]
Signed-off-by: John Stultz <john.stultz@linaro.org>

diff --git a/drivers/rtc/rtc-mxc.c b/drivers/rtc/rtc-mxc.c
index 826ab64..d814417 100644 (file)
--- a/drivers/rtc/rtc-mxc.c
+++ b/drivers/rtc/rtc-mxc.c
@@ -418,14 +418,6 @@ static int __init mxc_rtc_probe(struct platform_device *pdev)
                goto exit_put_clk;
        }
 
-       rtc = rtc_device_register(pdev->name, &pdev->dev, &mxc_rtc_ops,
-                                 THIS_MODULE);
-       if (IS_ERR(rtc)) {
-               ret = PTR_ERR(rtc);
-               goto exit_put_clk;
-       }
-
-       pdata->rtc = rtc;
        platform_set_drvdata(pdev, pdata);
 
        /* Configure and enable the RTC */
@@ -438,8 +430,19 @@ static int __init mxc_rtc_probe(struct platform_device *pdev)
                pdata->irq = -1;
        }
 
+       rtc = rtc_device_register(pdev->name, &pdev->dev, &mxc_rtc_ops,
+                                 THIS_MODULE);
+       if (IS_ERR(rtc)) {
+               ret = PTR_ERR(rtc);
+               goto exit_clr_drvdata;
+       }
+
+       pdata->rtc = rtc;
+
        return 0;
 
+exit_clr_drvdata:
+       platform_set_drvdata(pdev, NULL);
 exit_put_clk:
        clk_disable(pdata->clk);
        clk_put(pdata->clk);