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>

1 files changed, 11 insertions, 8 deletions

diff --git a/drivers/rtc/rtc-mxc.c b/drivers/rtc/rtc-mxc.c
index 826ab64a8fa9..d814417bee8c 100644
--- 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);