Commit 36d46cdb authored Dec 25, 2017 by Baolin Wang Committed by Alexandre Belloni Feb 13, 2018

rtc: Fix overflow when converting time64_t to rtc_time



If we convert one large time values to rtc_time, in the original formula
'days * 86400' can be overflowed in 'unsigned int' type to make the formula
get one incorrect remain seconds value. Thus we can use div_s64_rem()
function to avoid this situation.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

parent 29a1f599

drivers/rtc/rtc-lib.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -52,13 +52,11 @@ EXPORT_SYMBOL(rtc_year_days);
		*/
		void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
		{
		unsigned int month, year;
		unsigned long secs;
		unsigned int month, year, secs;
		int days;

		/* time must be positive */
		days = div_s64(time, 86400);
		secs = time - (unsigned int) days * 86400;
		days = div_s64_rem(time, 86400, &secs);

		/* day of the week, 1970-01-01 was a Thursday */
		tm->tm_wday = (days + 4) % 7;

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