rtc: Fix race when disable/enable UIE in rtc_set_time()

hulk inclusion
category: bugfix
bugzilla: 186781, https://gitee.com/openeuler/kernel/issues/I61CEW
CVE: NA

--------------------------------

When the RTC_SET_TIME and RTC_RD_TIME threads run in parallel,
there is no guarantee that uie_rtctimer.enabled is equal to the
previously read uie when executing rtc->ops->set_time.

Fix this by keeping reading uie state, disabling uie, setting
rtc time and enabling uie in critical sections.

Fixes: 7e7c005b ("rtc: disable uie before setting time and enable after")
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/rtc/interface.c

@@ -137,21 +137,19 @@ int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
 
 	rtc_subtract_offset(rtc, tm);
 
-#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
-	uie = rtc->uie_rtctimer.enabled || rtc->uie_irq_active;
-#else
+	err = mutex_lock_interruptible(&rtc->ops_lock);
+	if (err)
+		return err;
+
 	uie = rtc->uie_rtctimer.enabled;
-#endif
 	if (uie) {
-		err = rtc_update_irq_enable(rtc, 0);
-		if (err)
+		err = __rtc_update_irq_enable(rtc, 0);
+		if (err) {
+			mutex_unlock(&rtc->ops_lock);
 			return err;
+		}
 	}
 
-	err = mutex_lock_interruptible(&rtc->ops_lock);
-	if (err)
-		return err;
-
 	if (!rtc->ops)
 		err = -ENODEV;
 	else if (rtc->ops->set_time)
@@ -160,16 +158,14 @@ int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
 		err = -EINVAL;
 
 	pm_stay_awake(rtc->dev.parent);
+
+	if (uie)
+		err = __rtc_update_irq_enable(rtc, 1);
+
 	mutex_unlock(&rtc->ops_lock);
 	/* A timer might have just expired */
 	schedule_work(&rtc->irqwork);
 
-	if (uie) {
-		err = rtc_update_irq_enable(rtc, 1);
-		if (err)
-			return err;
-	}
-
 	trace_rtc_set_time(rtc_tm_to_time64(tm), err);
 	return err;
 }