8252997: Null-proofing for linker_md.c

Reviewed-by: sspitsyn

Author: Adam Farley

src/jdk.jdwp.agent/unix/native/libjdwp/linker_md.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2020, 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
@@ -49,11 +49,12 @@ static void dll_build_name(char* buffer, size_t buflen,
     *buffer = '\0';
 
     paths_copy = jvmtiAllocate((int)strlen(paths) + 1);
-    strcpy(paths_copy, paths);
     if (paths_copy == NULL) {
         return;
     }
 
+    strcpy(paths_copy, paths);
+
     next_token = NULL;
     path = strtok_r(paths_copy, PATH_SEPARATOR, &next_token);
 

src/jdk.jdwp.agent/windows/native/libjdwp/linker_md.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2020, 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
@@ -46,11 +46,12 @@ static void dll_build_name(char* buffer, size_t buflen,
     *buffer = '\0';
 
     paths_copy = jvmtiAllocate((int)strlen(paths) + 1);
-    strcpy(paths_copy, paths);
     if (paths_copy == NULL) {
         return;
     }
 
+    strcpy(paths_copy, paths);
+
     next_token = NULL;
     path = strtok_s(paths_copy, PATH_SEPARATOR, &next_token);