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gdatetime: Fix overflow checks when constructing from timestamps

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GDateTime does overflow checks to see if the timestamp being passed in
is too big to be represented. However, it only does those after
converting from a timestamp to an interval, which involves some
multiplications and additions — and hence can overflow, and cause the
later bounds check to erroneously succeed. This results in a non-NULL
GDateTime being returned which represents completely the wrong date.

Fix the overflow checks (do them earlier) and add some unit tests.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=782089
This commit is contained in:
Philip Withnall 2017-05-02 23:33:23 +01:00
parent 17395d79eb
commit 9374ecc3cb
2 changed files with 93 additions and 0 deletions
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9
glib/gdatetime.c
View File

@ -129,6 +129,8 @@ struct _GDateTime
((instant)/USEC_PER_SECOND - UNIX_EPOCH_START * SEC_PER_DAY)
#define UNIX_TO_INSTANT(unix) \
(((unix) + UNIX_EPOCH_START * SEC_PER_DAY) * USEC_PER_SECOND)
#define UNIX_TO_INSTANT_IS_VALID(unix) \
((gint64) (unix) <= INSTANT_TO_UNIX (G_MAXINT64))
#define DAYS_IN_4YEARS 1461 /* days in 4 years */
#define DAYS_IN_100YEARS 36524 /* days in 100 years */
@ -650,6 +652,10 @@ static GDateTime *
g_date_time_new_from_timeval (GTimeZone *tz,
const GTimeVal *tv)
{
if ((gint64) tv->tv_sec > G_MAXINT64 - 1 ||
!UNIX_TO_INSTANT_IS_VALID ((gint64) tv->tv_sec + 1))
return NULL;
return g_date_time_from_instant (tz, tv->tv_usec +
UNIX_TO_INSTANT (tv->tv_sec));
}
@ -679,6 +685,9 @@ static GDateTime *
g_date_time_new_from_unix (GTimeZone *tz,
gint64 secs)
{
if (!UNIX_TO_INSTANT_IS_VALID (secs))
return NULL;
return g_date_time_from_instant (tz, UNIX_TO_INSTANT (secs));
}

84
glib/tests/gdatetime.c
View File

@ -139,6 +139,23 @@ test_GDateTime_new_from_unix (void)
g_date_time_unref (dt);
}
/* Check that trying to create a #GDateTime too far in the future reliably
* fails. Previously, the checks for this overflowed and it silently returned
* an incorrect #GDateTime. */
static void
test_GDateTime_new_from_unix_overflow (void)
{
GDateTime *dt;
g_test_bug ("782089");
dt = g_date_time_new_from_unix_utc (G_MAXINT64);
g_assert_null (dt);
dt = g_date_time_new_from_unix_local (G_MAXINT64);
g_assert_null (dt);
}
static void
test_GDateTime_invalid (void)
{
@ -353,6 +370,71 @@ test_GDateTime_new_from_timeval (void)
g_date_time_unref (dt);
}
static gint64
find_maximum_supported_tv_sec (void)
{
glong highest_success = 0, lowest_failure = G_MAXLONG;
GTimeVal tv;
tv.tv_usec = 0;
while (highest_success < lowest_failure - 1)
{
GDateTime *dt;
tv.tv_sec = (highest_success + lowest_failure) / 2;
dt = g_date_time_new_from_timeval_utc (&tv);
if (dt != NULL)
{
highest_success = tv.tv_sec;
g_date_time_unref (dt);
}
else
{
lowest_failure = tv.tv_sec;
}
}
return highest_success;
}
/* Check that trying to create a #GDateTime too far in the future reliably
* fails. With a #GTimeVal, this is subtle, as the tv_usec are added into the
* calculation part-way through. */
static void
test_GDateTime_new_from_timeval_overflow (void)
{
GDateTime *dt;
GTimeVal tv;
g_test_bug ("782089");
tv.tv_sec = G_MAXLONG;
tv.tv_usec = 0;
dt = g_date_time_new_from_timeval_utc (&tv);
g_assert_null (dt);
dt = g_date_time_new_from_timeval_local (&tv);
g_assert_null (dt);
tv.tv_sec = find_maximum_supported_tv_sec ();
tv.tv_usec = G_USEC_PER_SEC - 1;
g_test_message ("Maximum supported GTimeVal.tv_sec = %lu", tv.tv_sec);
dt = g_date_time_new_from_timeval_utc (&tv);
g_assert_nonnull (dt);
g_date_time_unref (dt);
tv.tv_sec++;
tv.tv_usec = 0;
dt = g_date_time_new_from_timeval_utc (&tv);
g_assert_null (dt);
}
static void
test_GDateTime_new_from_timeval_utc (void)
{
@ -1652,8 +1734,10 @@ main (gint argc,
g_test_add_func ("/GDateTime/hash", test_GDateTime_hash);
g_test_add_func ("/GDateTime/new_from_unix", test_GDateTime_new_from_unix);
g_test_add_func ("/GDateTime/new_from_unix_utc", test_GDateTime_new_from_unix_utc);
g_test_add_func ("/GDateTime/new_from_unix/overflow", test_GDateTime_new_from_unix_overflow);
g_test_add_func ("/GDateTime/new_from_timeval", test_GDateTime_new_from_timeval);
g_test_add_func ("/GDateTime/new_from_timeval_utc", test_GDateTime_new_from_timeval_utc);
g_test_add_func ("/GDateTime/new_from_timeval/overflow", test_GDateTime_new_from_timeval_overflow);
g_test_add_func ("/GDateTime/new_full", test_GDateTime_new_full);
g_test_add_func ("/GDateTime/now", test_GDateTime_now);
g_test_add_func ("/GDateTime/printf", test_GDateTime_printf);