Check bounds.

Author: hoolioh

tracer/src/Datadog.Trace/LibDatadog/CString.cs

@@ -35,13 +35,23 @@ internal CString(string? str)
                 {
                     try
                     {
-                        Length = (nuint)encoding.GetBytes(strPtr, str.Length, (byte*)Ptr, maxBytesCount);
+                        int bytesWritten = (nuint)encoding.GetBytes(strPtr, str.Length, (byte*)Ptr, maxBytesCount);
+                        if (bytesWritten < 0 || bytesWritten > maxBytesCount)
+                        {
+                            Marshal.FreeHGlobal(Ptr);
+                            Ptr = IntPtr.Zero;
+                            Length = 0;
+                            return;
+                        }
+
+                        Length = (nuint)bytesWritten
                         *((byte*)Ptr + Length) = 0; // Add null terminator
                     }
                     catch
                     {
                         Marshal.FreeHGlobal(Ptr);
                         Ptr = IntPtr.Zero;
+                        Length = 0;
                     }
                 }
             }