From 4c9ef1a31bc41cd4af5880bb04761c9893c770dc Mon Sep 17 00:00:00 2001
From: Frank Tang <ftang@chromium.org>
Date: Thu, 19 Dec 2024 16:26:45 -0800
Subject: [PATCH] ICU-22962 Fix int overflow in
 Calendar::handleComputeJulianDay

---
 icu4c/source/i18n/calendar.cpp         |  7 ++++++-
 icu4c/source/test/intltest/caltest.cpp | 14 ++++++++++++++
 icu4c/source/test/intltest/caltest.h   |  1 +
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/icu4c/source/i18n/calendar.cpp b/icu4c/source/i18n/calendar.cpp
index c3643a986896..1dcf08a2eaf7 100644
--- a/icu4c/source/i18n/calendar.cpp
+++ b/icu4c/source/i18n/calendar.cpp
@@ -3607,7 +3607,12 @@ int32_t Calendar::handleComputeJulianDay(UCalendarDateFields bestField, UErrorCo
                     fprintf(stderr, "%s:%d - y=%d, y-1=%d doy%d, njd%d (C.F. %d)\n",
                         __FILE__, __LINE__, year, year-1, testDate, julianDay+testDate, nextJulianDay);
 #endif
-                    if(julianDay+testDate > nextJulianDay) { // is it past Dec 31?  (nextJulianDay is day BEFORE year+1's  Jan 1)
+                    if (uprv_add32_overflow(julianDay, testDate, &testDate)) {
+                        status = U_ILLEGAL_ARGUMENT_ERROR;
+                        return 0;
+                    }
+
+                    if(testDate > nextJulianDay) { // is it past Dec 31?  (nextJulianDay is day BEFORE year+1's  Jan 1)
                         // Fire up the calculating engines.. retry YWOY = (year-1)
                         int32_t prevYear;
                         if (uprv_add32_overflow(year, -1, &prevYear)) {
diff --git a/icu4c/source/test/intltest/caltest.cpp b/icu4c/source/test/intltest/caltest.cpp
index 83b410967c4b..121170857798 100644
--- a/icu4c/source/test/intltest/caltest.cpp
+++ b/icu4c/source/test/intltest/caltest.cpp
@@ -193,6 +193,7 @@ void CalendarTest::runIndexedTest( int32_t index, UBool exec, const char* &name,
 
     TESTCASE_AUTO(Test22633ChineseOverflow);
     TESTCASE_AUTO(Test22962ChineseOverflow);
+    TESTCASE_AUTO(Test22962BuddhistOverflow);
     TESTCASE_AUTO(Test22633IndianOverflow);
     TESTCASE_AUTO(Test22633IslamicUmalquraOverflow);
     TESTCASE_AUTO(Test22633PersianOverflow);
@@ -5665,6 +5666,19 @@ void CalendarTest::Test22633ChineseOverflow() {
     assertTrue("Should return falure", U_FAILURE(status));
 }
 
+void CalendarTest::Test22962BuddhistOverflow() {
+    UErrorCode status = U_ZERO_ERROR;
+    LocalPointer<Calendar> cal(Calendar::createInstance(Locale("en@calendar=uddhist"), status), status);
+    U_ASSERT(U_SUCCESS(status));
+    cal->clear();
+    cal->set(UCAL_WEEK_OF_YEAR, 1666136);
+    cal->set(UCAL_YEAR, -1887379272);
+    cal->fieldDifference(
+        261830011167902373443927125260580558779842815957727840993886210772873194951140935848493861585917165011373697198856398176256.000000,
+        UCAL_YEAR_WOY, status);
+    assertTrue("Should return falure", U_FAILURE(status));
+}
+
 void CalendarTest::Test22962ChineseOverflow() {
     UErrorCode status = U_ZERO_ERROR;
     LocalPointer<Calendar> cal(Calendar::createInstance(Locale("en@calendar=chinese"), status), status);
diff --git a/icu4c/source/test/intltest/caltest.h b/icu4c/source/test/intltest/caltest.h
index c83c0ffe0440..068db75b56f2 100644
--- a/icu4c/source/test/intltest/caltest.h
+++ b/icu4c/source/test/intltest/caltest.h
@@ -336,6 +336,7 @@ class CalendarTest: public CalendarTimeZoneTest {
     void TestRollWeekOfYear();
     void Test22633ChineseOverflow();
     void Test22962ChineseOverflow();
+    void Test22962BuddhistOverflow();
     void Test22633IndianOverflow();
     void Test22633IslamicUmalquraOverflow();
     void Test22633PersianOverflow();