8221530: Caller sensitive methods not handling caller = null when invoked by JNI code with no java frames on stack

Reviewed-by: alanb, dholmes, sundar

src/java.base/share/classes/java/lang/reflect/AccessibleObject.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2019, 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
@@ -56,7 +56,10 @@ import sun.security.util.SecurityConstants;
  * {@code Field}s, {@code Method}s, or {@code Constructor}s are used to get or
  * set fields, to invoke methods, or to create and initialize new instances of
  * classes, respectively. Every reflected object checks that the code using it
- * is in an appropriate class, package, or module. </p>
+ * is in an appropriate class, package, or module. The check when invoked by
+ * <a href="{@docRoot}/../specs/jni/index.html">JNI code</a> with no Java
+ * class on the stack only succeeds if the member and the declaring class are
+ * public, and the class is in a package that is exported to all modules. </p>
  *
  * <p> The one variation from Java language access control is that the checks
  * by reflected objects assume readability. That is, the module containing
@@ -670,6 +673,13 @@ public class AccessibleObject implements AnnotatedElement {
     private boolean slowVerifyAccess(Class<?> caller, Class<?> memberClass,
                                      Class<?> targetClass, int modifiers)
     {
+
+        if (caller == null) {
+            // No caller frame when a native thread attaches to the VM
+            // only allow access to a public accessible member
+            return Reflection.verifyPublicMemberAccess(memberClass, modifiers);
+        }
+
         if (!Reflection.verifyMemberAccess(caller, memberClass, targetClass, modifiers)) {
             // access denied
             return false;

src/java.base/share/classes/jdk/internal/reflect/Reflection.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2019, 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
@@ -122,6 +122,9 @@ public class Reflection {
                                              Class<?> targetClass,
                                              int modifiers)
     {
+        Objects.requireNonNull(currentClass);
+        Objects.requireNonNull(memberClass);
+
         if (currentClass == memberClass) {
             // Always succeeds
             return true;
@@ -201,6 +204,22 @@ public class Reflection {
         return true;
     }
 
+    /*
+     * Verify if a member is public and memberClass is a public type
+     * in a package that is unconditionally exported and
+     * return {@code true}if it is granted.
+     *
+     * @param memberClass the declaring class of the member being accessed
+     * @param modifiers the member's access modifiers
+     * @return {@code true} if the member is public and in a publicly accessible type
+     */
+    public static boolean verifyPublicMemberAccess(Class<?> memberClass, int modifiers) {
+        Module m = memberClass.getModule();
+        return Modifier.isPublic(modifiers)
+            && m.isExported(memberClass.getPackageName())
+            && Modifier.isPublic(Reflection.getClassAccessFlags(memberClass));
+    }
+
     /**
      * Returns {@code true} if memberClass's module exports memberClass's
      * package to currentModule.
@@ -325,8 +344,10 @@ public class Reflection {
                                                                    Class<?> memberClass,
                                                                    Class<?> targetClass,
                                                                    int modifiers)
-        throws IllegalAccessException
     {
+        if (currentClass == null)
+            return newIllegalAccessException(memberClass, modifiers);
+
         String currentSuffix = "";
         String memberSuffix = "";
         Module m1 = currentClass.getModule();
@@ -355,6 +376,36 @@ public class Reflection {
         return new IllegalAccessException(msg);
     }
 
+    /**
+     * Returns an IllegalAccessException with an exception message where
+     * there is no caller frame.
+     */
+    private static IllegalAccessException newIllegalAccessException(Class<?> memberClass,
+                                                                    int modifiers)
+    {
+        String memberSuffix = "";
+        Module m2 = memberClass.getModule();
+        if (m2.isNamed())
+            memberSuffix = " (in " + m2 + ")";
+
+        String memberPackageName = memberClass.getPackageName();
+
+        String msg = "JNI attached native thread (null caller frame) cannot access ";
+        if (m2.isExported(memberPackageName)) {
+
+            // module access okay so include the modifiers in the message
+            msg += "a member of " + memberClass + memberSuffix +
+                " with modifiers \"" + Modifier.toString(modifiers) + "\"";
+
+        } else {
+            // module access failed
+            msg += memberClass + memberSuffix+ " because "
+                + m2 + " does not export " + memberPackageName;
+        }
+
+        return new IllegalAccessException(msg);
+    }
+
     /**
      * Returns true if {@code currentClass} and {@code memberClass}
      * are nestmates - that is, if they have the same nesthost as