[Qemu-devel] [PATCH 1/3] rtc: fix overflow in mktimegm

[Paolo Bonzini <pbonzini@redhat.com>]

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>
---
 cutils.c         |  2 +-
 tests/rtc-test.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 file modificati, 46 inserzioni(+). 1 rimozione(-)

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;
diff --git a/tests/rtc-test.c b/tests/rtc-test.c
index f23ac3a..2b9aa63 100644
--- a/tests/rtc-test.c
+++ b/tests/rtc-test.c
@@ -179,6 +179,50 @@ static void check_time(int wiggle)
 
 static int wiggle = 2;
 
+static void set_year(void)
+{
+    /* Set BCD mode */
+    cmos_write(RTC_REG_B, cmos_read(RTC_REG_B) & ~REG_B_DM);
+    cmos_write(RTC_REG_A, 0x76);
+    cmos_write(RTC_YEAR, 0x11);
+    cmos_write(RTC_MONTH, 0x02);
+    cmos_write(RTC_DAY_OF_MONTH, 0x02);
+    cmos_write(RTC_HOURS, 0x02);
+    cmos_write(RTC_MINUTES, 0x04);
+    cmos_write(RTC_SECONDS, 0x58);
+    cmos_write(RTC_REG_A, 0x26);
+
+    g_assert_cmpint(cmos_read(RTC_HOURS), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_MINUTES), ==, 0x04);
+    g_assert_cmpint(cmos_read(RTC_SECONDS), >=, 0x58);
+    g_assert_cmpint(cmos_read(RTC_DAY_OF_MONTH), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_MONTH), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_YEAR), ==, 0x11);
+
+    /* Set a date in 2080 to ensure there is no year-2038 overflow.  */
+    cmos_write(RTC_REG_A, 0x76);
+    cmos_write(RTC_YEAR, 0x80);
+    cmos_write(RTC_REG_A, 0x26);
+
+    g_assert_cmpint(cmos_read(RTC_HOURS), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_MINUTES), ==, 0x04);
+    g_assert_cmpint(cmos_read(RTC_SECONDS), >=, 0x58);
+    g_assert_cmpint(cmos_read(RTC_DAY_OF_MONTH), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_MONTH), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_YEAR), ==, 0x80);
+
+    cmos_write(RTC_REG_A, 0x76);
+    cmos_write(RTC_YEAR, 0x11);
+    cmos_write(RTC_REG_A, 0x26);
+
+    g_assert_cmpint(cmos_read(RTC_HOURS), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_MINUTES), ==, 0x04);
+    g_assert_cmpint(cmos_read(RTC_SECONDS), >=, 0x58);
+    g_assert_cmpint(cmos_read(RTC_DAY_OF_MONTH), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_MONTH), ==, 0x02);
+    g_assert_cmpint(cmos_read(RTC_YEAR), ==, 0x11);
+}
+
 static void bcd_check_time(void)
 {
     /* Set BCD mode */
@@ -269,6 +313,7 @@ int main(int argc, char **argv)
     qtest_add_func("/rtc/bcd/check-time", bcd_check_time);
     qtest_add_func("/rtc/dec/check-time", dec_check_time);
     qtest_add_func("/rtc/alarm-time", alarm_time);
+    qtest_add_func("/rtc/set-year", set_year);
     qtest_add_func("/rtc/fuzz-registers", fuzz_registers);
     ret = g_test_run();
 
-- 
1.7.12