linux-kernel - [PATCH] rtc: cmos: initialize rtc time when reading alarm

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Message-Id: <20200813154020.1.Iaf7638a2f2a87ff68d85fcb8dec615e41340c97f@changeid>
Date:   Thu, 13 Aug 2020 15:41:34 +1000
From:   Victor Ding <victording@...gle.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Victor Ding <victording@...gle.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-rtc@...r.kernel.org
Subject: [PATCH] rtc: cmos: initialize rtc time when reading alarm

cmos_read_alarm() may leave certain fields of a struct rtc_time
untouched; therefore, these fields contain garbage if not properly
initialized, leading to inconsistent values when converting into
time64_t.
This patch to set all fields of a struct rtc_time to -1 before calling
cmos_read_alarm().

Signed-off-by: Victor Ding <victording@...gle.com>
---

 drivers/rtc/rtc-cmos.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index bcc96ab7793f..c99af567780d 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -1006,6 +1006,7 @@ static int cmos_suspend(struct device *dev)
 			enable_irq_wake(cmos->irq);
 	}
 
+	memset(&cmos->saved_wkalrm.time, -1, sizeof(struct rtc_time));
 	cmos_read_alarm(dev, &cmos->saved_wkalrm);
 
 	dev_dbg(dev, "suspend%s, ctrl %02x\n",
@@ -1054,6 +1055,7 @@ static void cmos_check_wkalrm(struct device *dev)
 		return;
 	}
 
+	memset(&current_alarm.time, -1, sizeof(struct rtc_time));
 	cmos_read_alarm(dev, &current_alarm);
 	t_current_expires = rtc_tm_to_time64(&current_alarm.time);
 	t_saved_expires = rtc_tm_to_time64(&cmos->saved_wkalrm.time);
-- 
2.28.0.236.gb10cc79966-goog