From a33fe7e206d0c394440962acd360df3aa9b117c3 Mon Sep 17 00:00:00 2001
From: cuiweixie <cuiweixie@gmail.com>
Date: Fri, 12 Aug 2022 20:22:21 +0800
Subject: [PATCH] net/http: don't panic on very large MaxBytesReaderLimit Fixes
 #54408

---
 src/net/http/request.go      | 3 ++-
 src/net/http/request_test.go | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/net/http/request.go b/src/net/http/request.go
index cead91d3d44..a5531fe4f94 100644
--- a/src/net/http/request.go
+++ b/src/net/http/request.go
@@ -1168,7 +1168,8 @@ func (l *maxBytesReader) Read(p []byte) (n int, err error) {
 	// If they asked for a 32KB byte read but only 5 bytes are
 	// remaining, no need to read 32KB. 6 bytes will answer the
 	// question of the whether we hit the limit or go past it.
-	if int64(len(p)) > l.n+1 {
+	// 0 < len(p) < 2^63
+	if int64(len(p))-1 > l.n {
 		p = p[:l.n+1]
 	}
 	n, err = l.r.Read(p)
diff --git a/src/net/http/request_test.go b/src/net/http/request_test.go
index d285840c1ce..0f147845476 100644
--- a/src/net/http/request_test.go
+++ b/src/net/http/request_test.go
@@ -982,6 +982,12 @@ func TestMaxBytesReaderDifferentLimits(t *testing.T) {
 			wantN:   len(testStr),
 			wantErr: false,
 		},
+		10: { /* Issue 54408 */
+			limit:   int64(1<<63-1),
+			lenP:    len(testStr),
+			wantN:   len(testStr),
+			wantErr: false,
+		},
 	}
 	for i, tt := range tests {
 		rc := MaxBytesReader(nil, io.NopCloser(strings.NewReader(testStr)), tt.limit)