rtc/mc13783: fix use after free bug

This was introduced by v2.6.34-rc1~38:

	4c014e8 (rtc/mc13783: protect rtc {,un}registration by mc13783 lock)

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 10 deletions

diff --git a/drivers/rtc/rtc-mc13783.c b/drivers/rtc/rtc-mc13783.c
index d60c81b7b693..1379c7faa448 100644
--- a/drivers/rtc/rtc-mc13783.c
+++ b/drivers/rtc/rtc-mc13783.c
@@ -319,35 +319,38 @@ static int __devinit mc13783_rtc_probe(struct platform_device *pdev)
 {
         int ret;
         struct mc13783_rtc *priv;
+        struct mc13783 *mc13783;
         int rtcrst_pending;
 
         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
         if (!priv)
                 return -ENOMEM;
 
-        priv->mc13783 = dev_get_drvdata(pdev->dev.parent);
+        mc13783 = dev_get_drvdata(pdev->dev.parent);
+        priv->mc13783 = mc13783;
+
         platform_set_drvdata(pdev, priv);
 
-        mc13783_lock(priv->mc13783);
+        mc13783_lock(mc13783);
 
-        ret = mc13783_irq_request(priv->mc13783, MC13783_IRQ_RTCRST,
+        ret = mc13783_irq_request(mc13783, MC13783_IRQ_RTCRST,
                         mc13783_rtc_reset_handler, DRIVER_NAME, priv);
         if (ret)
                 goto err_reset_irq_request;
 
-        ret = mc13783_irq_status(priv->mc13783, MC13783_IRQ_RTCRST,
+        ret = mc13783_irq_status(mc13783, MC13783_IRQ_RTCRST,
                         NULL, &rtcrst_pending);
         if (ret)
                 goto err_reset_irq_status;
 
         priv->valid = !rtcrst_pending;
 
-        ret = mc13783_irq_request_nounmask(priv->mc13783, MC13783_IRQ_1HZ,
+        ret = mc13783_irq_request_nounmask(mc13783, MC13783_IRQ_1HZ,
                         mc13783_rtc_update_handler, DRIVER_NAME, priv);
         if (ret)
                 goto err_update_irq_request;
 
-        ret = mc13783_irq_request_nounmask(priv->mc13783, MC13783_IRQ_TODA,
+        ret = mc13783_irq_request_nounmask(mc13783, MC13783_IRQ_TODA,
                         mc13783_rtc_alarm_handler, DRIVER_NAME, priv);
         if (ret)
                 goto err_alarm_irq_request;
@@ -357,22 +360,22 @@ static int __devinit mc13783_rtc_probe(struct platform_device *pdev)
         if (IS_ERR(priv->rtc)) {
                 ret = PTR_ERR(priv->rtc);
 
-                mc13783_irq_free(priv->mc13783, MC13783_IRQ_TODA, priv);
+                mc13783_irq_free(mc13783, MC13783_IRQ_TODA, priv);
 err_alarm_irq_request:
 
-                mc13783_irq_free(priv->mc13783, MC13783_IRQ_1HZ, priv);
+                mc13783_irq_free(mc13783, MC13783_IRQ_1HZ, priv);
 err_update_irq_request:
 
 err_reset_irq_status:
 
-                mc13783_irq_free(priv->mc13783, MC13783_IRQ_RTCRST, priv);
+                mc13783_irq_free(mc13783, MC13783_IRQ_RTCRST, priv);
 err_reset_irq_request:
 
                 platform_set_drvdata(pdev, NULL);
                 kfree(priv);
         }
 
-        mc13783_unlock(priv->mc13783);
+        mc13783_unlock(mc13783);
 
         return ret;
 }