8362208: [8u] Buffer overflow in g1GCPhaseTimes.cpp::LineBuffer::_buffer

Reviewed-by: phh, stuefe

Author: SendaoYan

hotspot/src/share/vm/gc_implementation/g1/g1GCPhaseTimes.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -34,13 +34,17 @@
 class LineBuffer: public StackObj {
 
 private:
-  static const int BUFFER_LEN = 1024;
+  static const int BUFFER_LEN = 1024*3;
   static const int INDENT_CHARS = 3;
   char _buffer[BUFFER_LEN];
   int _indent_level;
   int _cur;
 
   void vappend(const char* format, va_list ap)  ATTRIBUTE_PRINTF(2, 0) {
+    if (_cur >= BUFFER_LEN) {
+      DEBUG_ONLY(warning("previous LineBuffer overflow, request ignored");)
+      return;
+    }
     int res = os::vsnprintf(&_buffer[_cur], BUFFER_LEN - _cur, format, ap);
     if (res > BUFFER_LEN) {
       DEBUG_ONLY(warning("buffer too small in LineBuffer");)