From f962f3a28c3b91cf79ee31891d9235e65e3b8513 Mon Sep 17 00:00:00 2001
From: Jun Kimura <junkxdev@gmail.com>
Date: Tue, 17 Nov 2020 19:42:06 +0900
Subject: [PATCH] Fix int64 overflow error for height comparison (#7944)

* fix int64 overflow for height comparison

* apply suggestions from review

Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>
---
 x/ibc/core/02-client/types/height.go      | 16 +++++++---------
 x/ibc/core/02-client/types/height_test.go |  3 +++
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/x/ibc/core/02-client/types/height.go b/x/ibc/core/02-client/types/height.go
index 72af4d56b2..ab156e80de 100644
--- a/x/ibc/core/02-client/types/height.go
+++ b/x/ibc/core/02-client/types/height.go
@@ -2,6 +2,7 @@ package types
 
 import (
 	"fmt"
+	"math/big"
 	"regexp"
 	"strconv"
 	"strings"
@@ -54,18 +55,15 @@ func (h Height) Compare(other exported.Height) int64 {
 	if !ok {
 		panic(fmt.Sprintf("cannot compare against invalid height type: %T. expected height type: %T", other, h))
 	}
-	var cmp int64
+	var a, b big.Int
 	if h.VersionNumber != height.VersionNumber {
-		cmp = int64(h.VersionNumber) - int64(height.VersionNumber)
+		a.SetUint64(h.VersionNumber)
+		b.SetUint64(height.VersionNumber)
 	} else {
-		cmp = int64(h.VersionHeight) - int64(height.VersionHeight)
+		a.SetUint64(h.VersionHeight)
+		b.SetUint64(height.VersionHeight)
 	}
-	if cmp < 0 {
-		return -1
-	} else if cmp > 0 {
-		return 1
-	}
-	return 0
+	return int64(a.Cmp(&b))
 }
 
 // LT Helper comparison function returns true if h < other
diff --git a/x/ibc/core/02-client/types/height_test.go b/x/ibc/core/02-client/types/height_test.go
index 33d33fd714..0bd8f0848f 100644
--- a/x/ibc/core/02-client/types/height_test.go
+++ b/x/ibc/core/02-client/types/height_test.go
@@ -1,6 +1,7 @@
 package types_test
 
 import (
+	"math"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -23,6 +24,8 @@ func TestCompareHeights(t *testing.T) {
 		{"version number 1 is greater", types.NewHeight(7, 5), types.NewHeight(4, 5), 1},
 		{"version height 1 is lesser", types.NewHeight(3, 4), types.NewHeight(3, 9), -1},
 		{"version height 1 is greater", types.NewHeight(3, 8), types.NewHeight(3, 3), 1},
+		{"version number is MaxUint64", types.NewHeight(math.MaxUint64, 1), types.NewHeight(0, 1), 1},
+		{"version height is MaxUint64", types.NewHeight(1, math.MaxUint64), types.NewHeight(1, 0), 1},
 		{"height is equal", types.NewHeight(4, 4), types.NewHeight(4, 4), 0},
 	}