queue-4.4/rtc-fix-overflow-when-converting-time64_t-to-rtc_time.patch

   1 From 36d46cdb43efea74043e29e2a62b13e9aca31452 Mon Sep 17 00:00:00 2001
   2 From: Baolin Wang <baolin.wang@linaro.org>
   3 Date: Mon, 25 Dec 2017 19:10:37 +0800
   4 Subject: rtc: Fix overflow when converting time64_t to rtc_time
   5
   6 From: Baolin Wang <baolin.wang@linaro.org>
   7
   8 commit 36d46cdb43efea74043e29e2a62b13e9aca31452 upstream.
   9
  10 If we convert one large time values to rtc_time, in the original formula
  11 'days * 86400' can be overflowed in 'unsigned int' type to make the formula
  12 get one incorrect remain seconds value. Thus we can use div_s64_rem()
  13 function to avoid this situation.
  14
  15 Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
  16 Acked-by: Arnd Bergmann <arnd@arndb.de>
  17 Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
  18 Signed-off-by: Arnd Bergmann <arnd@arndb.de>
  19 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  20
  21 ---
  22  drivers/rtc/rtc-lib.c |    6 ++----
  23  1 file changed, 2 insertions(+), 4 deletions(-)
  24
  25 --- a/drivers/rtc/rtc-lib.c
  26 +++ b/drivers/rtc/rtc-lib.c
  27 @@ -52,13 +52,11 @@ EXPORT_SYMBOL(rtc_year_days);
  28   */
  29  void rtc_time64_to_tm(time64_t time, struct rtc_time *tm)
  30  {
  31 -       unsigned int month, year;
  32 -       unsigned long secs;
  33 +       unsigned int month, year, secs;
  34         int days;
  35
  36         /* time must be positive */
  37 -       days = div_s64(time, 86400);
  38 -       secs = time - (unsigned int) days * 86400;
  39 +       days = div_s64_rem(time, 86400, &secs);
  40
  41         /* day of the week, 1970-01-01 was a Thursday */
  42         tm->tm_wday = (days + 4) % 7;