8227542: Manifest improved jar headers

Reviewed-by: andrew

src/share/classes/java/lang/instrument/package.html

@@ -38,6 +38,13 @@
 Provides services that allow Java programming language agents to instrument programs running on the JVM. 
 The mechanism for instrumentation is modification of the byte-codes of methods.
 
+<P>
+Note: developers/admininstrators are responsible for verifying the trustworthiness of
+content and structure of the Java Agents they deploy, since those are able to arbitrarily
+transform the bytecode from other JAR files. Since that happens after the Jars containing
+the bytecode have been verified as trusted, the trustworthiness of a Java Agent can determine
+the trust towards the entire program.
+
 <h2>Package Specification</h2>
 
 <P> 

src/share/instrument/InvocationAdapter.c

@@ -203,6 +203,17 @@ Agent_OnLoad(JavaVM *vm, char *tail, void * reserved) {
          */
         oldLen = (int)strlen(premainClass);
         newLen = modifiedUtf8LengthOfUtf8(premainClass, oldLen);
+        /*
+         * According to JVMS class name is represented as CONSTANT_Utf8_info,
+         * so its length is u2 (i.e. must be <= 0xFFFF).
+         */
+        if (newLen > 0xFFFF) {
+            fprintf(stderr, "-javaagent: Premain-Class value is too big\n");
+            free(jarfile);
+            if (options != NULL) free(options);
+            freeAttributes(attributes);
+            return JNI_ERR;
+        }
         if (newLen == oldLen) {
             premainClass = strdup(premainClass);
         } else {
@@ -362,6 +373,17 @@ Agent_OnAttach(JavaVM* vm, char *args, void * reserved) {
          */
         oldLen = strlen(agentClass);
         newLen = modifiedUtf8LengthOfUtf8(agentClass, oldLen);
+        /*
+         * According to JVMS class name is represented as CONSTANT_Utf8_info,
+         * so its length is u2 (i.e. must be <= 0xFFFF).
+         */
+        if (newLen > 0xFFFF) {
+            fprintf(stderr, "Agent-Class value is too big\n");
+            free(jarfile);
+            if (options != NULL) free(options);
+            freeAttributes(attributes);
+            return AGENT_ERROR_BADJAR;
+        }
         if (newLen == oldLen) {
             agentClass = strdup(agentClass);
         } else {