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    Subject[PATCH] rtc: Fix overflow when converting time64_t to rtc_time
    Date
    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>
    ---
    drivers/rtc/rtc-lib.c | 6 ++----
    1 file changed, 2 insertions(+), 4 deletions(-)

    diff --git a/drivers/rtc/rtc-lib.c b/drivers/rtc/rtc-lib.c
    index 1ae7da5..ad5bb21 100644
    --- a/drivers/rtc/rtc-lib.c
    +++ b/drivers/rtc/rtc-lib.c
    @@ -52,13 +52,11 @@ int rtc_year_days(unsigned int day, unsigned int month, unsigned int year)
    */
    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;
    --
    1.7.9.5
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