8025922: JNI access to Strings need to check if the value field is non-null

Reviewed-by: dholmes, dcubed

src/share/vm/prims/jni.cpp

@@ -3210,7 +3210,11 @@ JNI_QUICK_ENTRY(jsize, jni_GetStringLength(JNIEnv *env, jstring string))
   HOTSPOT_JNI_GETSTRINGLENGTH_ENTRY(
                                     env, string);
 #endif /* USDT2 */
-  jsize ret = java_lang_String::length(JNIHandles::resolve_non_null(string));
+  jsize ret = 0;
+  oop s = JNIHandles::resolve_non_null(string);
+  if (java_lang_String::value(s) != NULL) {
+    ret = java_lang_String::length(s);
+  }
 #ifndef USDT2
   DTRACE_PROBE1(hotspot_jni, GetStringLength__return, ret);
 #else /* USDT2 */
@@ -3230,11 +3234,13 @@ JNI_QUICK_ENTRY(const jchar*, jni_GetStringChars(
  HOTSPOT_JNI_GETSTRINGCHARS_ENTRY(
                                   env, string, (uintptr_t *) isCopy);
 #endif /* USDT2 */
+  jchar* buf = NULL;
   oop s = JNIHandles::resolve_non_null(string);
-  int s_len = java_lang_String::length(s);
   typeArrayOop s_value = java_lang_String::value(s);
+  if (s_value != NULL) {
+    int s_len = java_lang_String::length(s);
     int s_offset = java_lang_String::offset(s);
-  jchar* buf = NEW_C_HEAP_ARRAY_RETURN_NULL(jchar, s_len + 1, mtInternal);  // add one for zero termination
+    buf = NEW_C_HEAP_ARRAY_RETURN_NULL(jchar, s_len + 1, mtInternal);  // add one for zero termination
     /* JNI Specification states return NULL on OOM */
     if (buf != NULL) {
       if (s_len > 0) {
@@ -3246,6 +3252,7 @@ JNI_QUICK_ENTRY(const jchar*, jni_GetStringChars(
         *isCopy = JNI_TRUE;
       }
     }
+  }
 #ifndef USDT2
   DTRACE_PROBE1(hotspot_jni, GetStringChars__return, buf);
 #else /* USDT2 */
@@ -3313,7 +3320,11 @@ JNI_ENTRY(jsize, jni_GetStringUTFLength(JNIEnv *env, jstring string))
  HOTSPOT_JNI_GETSTRINGUTFLENGTH_ENTRY(
                                       env, string);
 #endif /* USDT2 */
-  jsize ret = java_lang_String::utf8_length(JNIHandles::resolve_non_null(string));
+  jsize ret = 0;
+  oop java_string = JNIHandles::resolve_non_null(string);
+  if (java_lang_String::value(java_string) != NULL) {
+    ret = java_lang_String::utf8_length(java_string);
+  }
 #ifndef USDT2
   DTRACE_PROBE1(hotspot_jni, GetStringUTFLength__return, ret);
 #else /* USDT2 */
@@ -3332,16 +3343,19 @@ JNI_ENTRY(const char*, jni_GetStringUTFChars(JNIEnv *env, jstring string, jboole
  HOTSPOT_JNI_GETSTRINGUTFCHARS_ENTRY(
                                      env, string, (uintptr_t *) isCopy);
 #endif /* USDT2 */
+  char* result = NULL;
   oop java_string = JNIHandles::resolve_non_null(string);
+  if (java_lang_String::value(java_string) != NULL) {
     size_t length = java_lang_String::utf8_length(java_string);
     /* JNI Specification states return NULL on OOM */
-  char* result = AllocateHeap(length + 1, mtInternal, 0, AllocFailStrategy::RETURN_NULL);
+    result = AllocateHeap(length + 1, mtInternal, 0, AllocFailStrategy::RETURN_NULL);
     if (result != NULL) {
       java_lang_String::as_utf8_string(java_string, result, (int) length + 1);
       if (isCopy != NULL) {
         *isCopy = JNI_TRUE;
       }
     }
+  }
 #ifndef USDT2
   DTRACE_PROBE1(hotspot_jni, GetStringUTFChars__return, result);
 #else /* USDT2 */

src/share/vm/prims/jniCheck.cpp

@@ -1324,18 +1324,19 @@ JNI_ENTRY_CHECKED(const jchar *,
     IN_VM(
       checkString(thr, str);
     )
+    jchar* newResult = NULL;
     const jchar *result = UNCHECKED()->GetStringChars(env,str,isCopy);
     assert (isCopy == NULL || *isCopy == JNI_TRUE, "GetStringChars didn't return a copy as expected");
-
+    if (result != NULL) {
       size_t len = UNCHECKED()->GetStringLength(env,str) + 1; // + 1 for NULL termination
       jint* tagLocation = (jint*) AllocateHeap(len * sizeof(jchar) + sizeof(jint), mtInternal);
       *tagLocation = STRING_TAG;
-    jchar* newResult = (jchar*) (tagLocation + 1);
+      newResult = (jchar*) (tagLocation + 1);
       memcpy(newResult, result, len * sizeof(jchar));
       // Avoiding call to UNCHECKED()->ReleaseStringChars() since that will fire unexpected dtrace probes
       // Note that the dtrace arguments for the allocated memory will not match up with this solution.
       FreeHeap((char*)result);
-
+    }
     functionExit(env);
     return newResult;
 JNI_END
@@ -1394,18 +1395,19 @@ JNI_ENTRY_CHECKED(const char *,
     IN_VM(
       checkString(thr, str);
     )
+    char* newResult = NULL;
     const char *result = UNCHECKED()->GetStringUTFChars(env,str,isCopy);
     assert (isCopy == NULL || *isCopy == JNI_TRUE, "GetStringUTFChars didn't return a copy as expected");
-
+    if (result != NULL) {
       size_t len = strlen(result) + 1; // + 1 for NULL termination
       jint* tagLocation = (jint*) AllocateHeap(len + sizeof(jint), mtInternal);
       *tagLocation = STRING_UTF_TAG;
-    char* newResult = (char*) (tagLocation + 1);
+      newResult = (char*) (tagLocation + 1);
       strcpy(newResult, result);
       // Avoiding call to UNCHECKED()->ReleaseStringUTFChars() since that will fire unexpected dtrace probes
       // Note that the dtrace arguments for the allocated memory will not match up with this solution.
       FreeHeap((char*)result, mtInternal);
-
+    }
     functionExit(env);
     return newResult;
 JNI_END