linux-kernel - [PATCH] rtc: wilco-ec: Sanitize values received from RTC

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Date:   Tue, 10 Sep 2019 16:19:29 +0100
From:   Nick Crews <ncrews@...omium.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Alessandro Zummo <a.zummo@...ertech.it>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Duncan Laurie <dlaurie@...gle.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Nick Crews <ncrews@...omium.org>
Subject: [PATCH] rtc: wilco-ec: Sanitize values received from RTC

Check that the time received from the RTC HW is valid,
otherwise the computation of rtc_year_days() in the next
line could, and sometimes does, crash the kernel.

While we're at it, fix the license to plain "GPL".

Signed-off-by: Nick Crews <ncrews@...omium.org>
---
 drivers/rtc/rtc-wilco-ec.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-wilco-ec.c b/drivers/rtc/rtc-wilco-ec.c
index 8ad4c4e6d557..0ccbf2dce832 100644
--- a/drivers/rtc/rtc-wilco-ec.c
+++ b/drivers/rtc/rtc-wilco-ec.c
@@ -110,8 +110,16 @@ static int wilco_ec_rtc_read(struct device *dev, struct rtc_time *tm)
 	tm->tm_mday	= rtc.day;
 	tm->tm_mon	= rtc.month - 1;
 	tm->tm_year	= rtc.year + (rtc.century * 100) - 1900;
-	tm->tm_yday	= rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
 
+	if (rtc_valid_tm(tm)) {
+		dev_warn(dev,
+			 "Time computed from EC RTC is invalid: sec=%d, min=%d, hour=%d, mday=%d, mon=%d, year=%d",
+			 tm->tm_sec, tm->tm_min, tm->tm_hour, tm->mday,
+			 tm->mon, tm->year);
+		return -EIO;
+	}
+
+	tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
 	/* Don't compute day of week, we don't need it. */
 	tm->tm_wday = -1;
 
@@ -188,5 +196,5 @@ module_platform_driver(wilco_ec_rtc_driver);
 
 MODULE_ALIAS("platform:rtc-wilco-ec");
 MODULE_AUTHOR("Nick Crews <ncrews@...omium.org>");
-MODULE_LICENSE("GPL v2");
+MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Wilco EC RTC driver");
-- 
2.11.0