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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>
This commit is contained in:
Baolin Wang 2017-12-25 19:10:37 +08:00 committed by Alexandre Belloni
parent 29a1f599c0
commit 36d46cdb43
1 changed files with 2 additions and 4 deletions
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6
drivers/rtc/rtc-lib.c
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@ -52,13 +52,11 @@ EXPORT_SYMBOL(rtc_year_days);
*/ */
void rtc_time64_to_tm(time64_t time, struct rtc_time *tm) void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
{ {
unsigned int month, year; unsigned int month, year, secs;
unsigned long secs;
int days; int days;
/* time must be positive */ /* time must be positive */
days = div_s64(time, 86400); days = div_s64_rem(time, 86400, &secs);
secs = time - (unsigned int) days * 86400;
/* day of the week, 1970-01-01 was a Thursday */ /* day of the week, 1970-01-01 was a Thursday */
tm->tm_wday = (days + 4) % 7; tm->tm_wday = (days + 4) % 7;