rtc: fix overflow in mktimegm

When setting a date in 1980, Linux is actually disregarding the century
byte and setting the year to 2080.  This causes a year-2038 overflow
in mktimegm.  Fix this by doing the days-to-seconds computation in
64-bit math.

Reported-by: Lucas Meneghel Rodrigues <lookkas@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/cutils.c b/cutils.c
index 8ef648f..8edd8fa 100644
--- a/cutils.c
+++ b/cutils.c
@@ -115,7 +115,7 @@ time_t mktimegm(struct tm *tm)
         m += 12;
         y--;
     }
-    t = 86400 * (d + (153 * m - 457) / 5 + 365 * y + y / 4 - y / 100 + 
+    t = 86400ULL * (d + (153 * m - 457) / 5 + 365 * y + y / 4 - y / 100 + 
                  y / 400 - 719469);
     t += 3600 * tm->tm_hour + 60 * tm->tm_min + tm->tm_sec;
     return t;