Fix vulnerability in MemoryIntArray

am: 1181f448c1

Change-Id: I4217066be49bb9525e945f110c22eb864ec6c212

core/java/android/util/MemoryIntArray.java

@@ -35,13 +35,13 @@ import java.util.UUID;
  * each other.
  * <p>
  * The data structure is designed to have one owner process that can
- * read/write. There may be multiple client processes that can only read or
+ * read/write. There may be multiple client processes that can only read.
- * read/write depending how the data structure was configured when
+ * The owner process is the process that created the array. The shared
- * instantiated. The owner process is the process that created the array.
+ * memory is pinned (not reclaimed by the system) until the owning process
- * The shared memory is pinned (not reclaimed by the system) until the
+ * dies or the data structure is closed. This class is <strong>not</strong>
- * owning process dies or the data structure is closed. This class
+ * thread safe. You should not interact with an instance of this class
- * is <strong>not</strong> thread safe. You should not interact with
+ * once it is closed. If you pass back to the owner process an instance
- * an instance of this class once it is closed.
+ * it will be read only even in the owning process.
  * </p>
  *
  * @hide
@@ -51,8 +51,7 @@ public final class MemoryIntArray implements Parcelable, Closeable {
 
     private static final int MAX_SIZE = 1024;
 
-    private final int mOwnerPid;
+    private final boolean mIsOwner;
-    private final boolean mClientWritable;
     private final long mMemoryAddr;
     private int mFd;
 
@@ -64,31 +63,24 @@ public final class MemoryIntArray implements Parcelable, Closeable {
      * @param clientWritable Whether other processes can write to the array.
      * @throws IOException If an error occurs while accessing the shared memory.
      */
-    public MemoryIntArray(int size, boolean clientWritable) throws IOException {
+    public MemoryIntArray(int size) throws IOException {
         if (size > MAX_SIZE) {
             throw new IllegalArgumentException("Max size is " + MAX_SIZE);
         }
-        mOwnerPid = Process.myPid();
+        mIsOwner = true;
-        mClientWritable = clientWritable;
         final String name = UUID.randomUUID().toString();
         mFd = nativeCreate(name, size);
-        mMemoryAddr = nativeOpen(mFd, true, clientWritable);
+        mMemoryAddr = nativeOpen(mFd, mIsOwner);
     }
 
     private MemoryIntArray(Parcel parcel) throws IOException {
-        mOwnerPid = parcel.readInt();
+        mIsOwner = false;
-        mClientWritable = (parcel.readInt() == 1);
         ParcelFileDescriptor pfd = parcel.readParcelable(null);
         if (pfd == null) {
             throw new IOException("No backing file descriptor");
         }
         mFd = pfd.detachFd();
-        final long memoryAddress = parcel.readLong();
+        mMemoryAddr = nativeOpen(mFd, mIsOwner);
-        if (isOwner()) {
-            mMemoryAddr = memoryAddress;
-        } else {
-            mMemoryAddr = nativeOpen(mFd, false, mClientWritable);
-        }
     }
 
     /**
@@ -96,7 +88,7 @@ public final class MemoryIntArray implements Parcelable, Closeable {
      */
     public boolean isWritable() {
         enforceNotClosed();
-        return isOwner() || mClientWritable;
+        return mIsOwner;
     }
 
     /**
@@ -109,7 +101,7 @@ public final class MemoryIntArray implements Parcelable, Closeable {
     public int get(int index) throws IOException {
         enforceNotClosed();
         enforceValidIndex(index);
-        return nativeGet(mFd, mMemoryAddr, index, isOwner());
+        return nativeGet(mFd, mMemoryAddr, index);
     }
 
     /**
@@ -125,7 +117,7 @@ public final class MemoryIntArray implements Parcelable, Closeable {
         enforceNotClosed();
         enforceWritable();
         enforceValidIndex(index);
-        nativeSet(mFd, mMemoryAddr, index, value, isOwner());
+        nativeSet(mFd, mMemoryAddr, index, value);
     }
 
     /**
@@ -146,7 +138,7 @@ public final class MemoryIntArray implements Parcelable, Closeable {
     @Override
     public void close() throws IOException {
         if (!isClosed()) {
-            nativeClose(mFd, mMemoryAddr, isOwner());
+            nativeClose(mFd, mMemoryAddr, mIsOwner);
             mFd = -1;
         }
     }
@@ -173,10 +165,7 @@ public final class MemoryIntArray implements Parcelable, Closeable {
     public void writeToParcel(Parcel parcel, int flags) {
         ParcelFileDescriptor pfd = ParcelFileDescriptor.adoptFd(mFd);
         try {
-            parcel.writeInt(mOwnerPid);
-            parcel.writeInt(mClientWritable ? 1 : 0);
             parcel.writeParcelable(pfd, flags & ~Parcelable.PARCELABLE_WRITE_RETURN_VALUE);
-            parcel.writeLong(mMemoryAddr);
         } finally {
             pfd.detachFd();
         }
@@ -202,10 +191,6 @@ public final class MemoryIntArray implements Parcelable, Closeable {
         return mFd;
     }
 
-    private boolean isOwner() {
-        return mOwnerPid == Process.myPid();
-    }
-
     private void enforceNotClosed() {
         if (isClosed()) {
             throw new IllegalStateException("cannot interact with a closed instance");
@@ -227,10 +212,10 @@ public final class MemoryIntArray implements Parcelable, Closeable {
     }
 
     private native int nativeCreate(String name, int size);
-    private native long nativeOpen(int fd, boolean owner, boolean writable);
+    private native long nativeOpen(int fd, boolean owner);
     private native void nativeClose(int fd, long memoryAddr, boolean owner);
-    private native int nativeGet(int fd, long memoryAddr, int index, boolean owner);
+    private native int nativeGet(int fd, long memoryAddr, int index);
-    private native void nativeSet(int fd, long memoryAddr, int index, int value, boolean owner);
+    private native void nativeSet(int fd, long memoryAddr, int index, int value);
     private native int nativeSize(int fd);
 
     /**
@@ -247,8 +232,7 @@ public final class MemoryIntArray implements Parcelable, Closeable {
             try {
                 return new MemoryIntArray(parcel);
             } catch (IOException ioe) {
-                Log.e(TAG, "Error unparceling MemoryIntArray");
+                throw new IllegalArgumentException("Error unparceling MemoryIntArray");
-                return null;
             }
         }
 

core/jni/android_util_MemoryIntArray.cpp

@@ -54,7 +54,7 @@ static jint android_util_MemoryIntArray_create(JNIEnv* env, jobject clazz, jstri
 }
 
 static jlong android_util_MemoryIntArray_open(JNIEnv* env, jobject clazz, jint fd,
-    jboolean owner, jboolean writable)
+    jboolean owner)
 {
     if (fd < 0) {
         jniThrowException(env, "java/io/IOException", "bad file descriptor");
@@ -67,19 +67,35 @@ static jlong android_util_MemoryIntArray_open(JNIEnv* env, jobject clazz, jint f
         return -1;
     }
 
-    int protMode = (owner || writable) ? (PROT_READ | PROT_WRITE) : PROT_READ;
+    // IMPORTANT: Ashmem allows the caller to change its size until
+    // it is memory mapped for the first time which lazily creates
+    // the underlying VFS file. So the size we get above may not
+    // reflect the size of the underlying shared memory region. Therefore,
+    // we first memory map to set the size in stone an verify if
+    // the underlying ashmem region has the same size as the one we
+    // memory mapped. This is critical as we use the underlying
+    // ashmem size for boundary checks and memory unmapping.
+    int protMode = owner ? (PROT_READ | PROT_WRITE) : PROT_READ;
     void* ashmemAddr = mmap(NULL, ashmemSize, protMode, MAP_SHARED, fd, 0);
     if (ashmemAddr == MAP_FAILED) {
         jniThrowException(env, "java/io/IOException", "cannot mmap ashmem");
         return -1;
     }
 
+    // Check if the mapped size is the same as the ashmem region.
+    int mmapedSize = ashmem_get_size_region(fd);
+    if (mmapedSize != ashmemSize) {
+        munmap(reinterpret_cast<void *>(ashmemAddr), ashmemSize);
+        jniThrowException(env, "java/io/IOException", "bad file descriptor");
+        return -1;
+    }
+
     if (owner) {
         int size = ashmemSize / sizeof(std::atomic_int);
         new (ashmemAddr) std::atomic_int[size];
     }
 
-    if (owner && !writable) {
+    if (owner) {
         int setProtResult = ashmem_set_prot_region(fd, PROT_READ);
         if (setProtResult < 0) {
             jniThrowException(env, "java/io/IOException", "cannot set ashmem prot mode");
@@ -121,7 +137,7 @@ static void android_util_MemoryIntArray_close(JNIEnv* env, jobject clazz, jint f
 }
 
 static jint android_util_MemoryIntArray_get(JNIEnv* env, jobject clazz,
-        jint fd, jlong address, jint index, jboolean owner)
+        jint fd, jlong address, jint index)
 {
     if (fd < 0) {
         jniThrowException(env, "java/io/IOException", "bad file descriptor");
@@ -138,7 +154,7 @@ static jint android_util_MemoryIntArray_get(JNIEnv* env, jobject clazz,
 }
 
 static void android_util_MemoryIntArray_set(JNIEnv* env, jobject clazz,
-        jint fd, jlong address, jint index, jint newValue, jboolean owner)
+        jint fd, jlong address, jint index, jint newValue)
 {
     if (fd < 0) {
         jniThrowException(env, "java/io/IOException", "bad file descriptor");
@@ -171,10 +187,10 @@ static jint android_util_MemoryIntArray_size(JNIEnv* env, jobject clazz, jint fd
 
 static const JNINativeMethod methods[] = {
     {"nativeCreate",  "(Ljava/lang/String;I)I", (void*)android_util_MemoryIntArray_create},
-    {"nativeOpen",  "(IZZ)J", (void*)android_util_MemoryIntArray_open},
+    {"nativeOpen",  "(IZ)J", (void*)android_util_MemoryIntArray_open},
     {"nativeClose", "(IJZ)V", (void*)android_util_MemoryIntArray_close},
-    {"nativeGet",  "(IJIZ)I", (void*)android_util_MemoryIntArray_get},
+    {"nativeGet",  "(IJI)I", (void*)android_util_MemoryIntArray_get},
-    {"nativeSet", "(IJIIZ)V", (void*) android_util_MemoryIntArray_set},
+    {"nativeSet", "(IJII)V", (void*) android_util_MemoryIntArray_set},
     {"nativeSize", "(I)I", (void*) android_util_MemoryIntArray_size},
 };
 

core/tests/utiltests/Android.mk

@@ -12,6 +12,8 @@ LOCAL_MODULE_TAGS := tests
 LOCAL_SRC_FILES := $(call all-java-files-under, src)
 LOCAL_SRC_FILES += src/android/util/IRemoteMemoryIntArray.aidl
 
+LOCAL_JNI_SHARED_LIBRARIES := libmemoryintarraytest libcutils libc++
+
 LOCAL_STATIC_JAVA_LIBRARIES := \
     android-support-test \
     mockito-target
@@ -23,3 +25,5 @@ LOCAL_PACKAGE_NAME := FrameworksUtilTests
 LOCAL_CERTIFICATE := platform
 
 include $(BUILD_PACKAGE)
+
+include $(call all-makefiles-under,$(LOCAL_PATH))

core/tests/utiltests/jni/Android.mk

@@ -0,0 +1,32 @@
+# Copyright 2016 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License..
+
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := libmemoryintarraytest
+
+LOCAL_SRC_FILES := \
+    registration.cpp \
+    android_util_MemoryIntArrayTest.cpp
+
+LOCAL_CFLAGS += -include bionic/libc/kernel/uapi/linux/types.h
+
+LOCAL_SHARED_LIBRARIES := libcutils
+
+LOCAL_CLANG := true
+
+LOCAL_CPPFLAGS := -Werror
+
+include $(BUILD_SHARED_LIBRARY)

core/tests/utiltests/jni/android_util_MemoryIntArrayTest.cpp

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <atomic>
+#include <jni.h>
+#include <cutils/ashmem.h>
+#include <linux/ashmem.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+
+jint android_util_MemoryIntArrayTest_createAshmem(__attribute__((unused)) JNIEnv* env,
+        __attribute__((unused)) jobject clazz,
+        jstring name, jint size)
+{
+
+    if (name == NULL) {
+        return -1;
+    }
+
+    if (size < 0) {
+        return -1;
+    }
+
+    const char* nameStr = env->GetStringUTFChars(name, NULL);
+    const int ashmemSize = sizeof(std::atomic_int) * size;
+    int fd = ashmem_create_region(nameStr, ashmemSize);
+    env->ReleaseStringUTFChars(name, nameStr);
+
+    if (fd < 0) {
+        return -1;
+    }
+
+    int setProtResult = ashmem_set_prot_region(fd, PROT_READ | PROT_WRITE);
+    if (setProtResult < 0) {
+        return -1;
+    }
+
+    return fd;
+}
+
+void android_util_MemoryIntArrayTest_setAshmemSize(__attribute__((unused)) JNIEnv* env,
+        __attribute__((unused)) jobject clazz, jint fd, jint size)
+{
+    if (fd < 0) {
+        return;
+    }
+
+    if (size < 0) {
+        return;
+    }
+
+    ioctl(fd, ASHMEM_SET_SIZE, size);
+}

core/tests/utiltests/jni/registration.cpp

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <jni.h>
+
+extern jint android_util_MemoryIntArrayTest_createAshmem(JNIEnv* env,
+        jobject clazz, jstring name, jint size);
+extern void android_util_MemoryIntArrayTest_setAshmemSize(JNIEnv* env,
+       jobject clazz, jint fd, jint size);
+
+extern "C" {
+    JNIEXPORT jint JNICALL Java_android_util_MemoryIntArrayTest_nativeCreateAshmem(
+            JNIEnv * env, jobject obj, jstring name, jint size);
+    JNIEXPORT void JNICALL Java_android_util_MemoryIntArrayTest_nativeSetAshmemSize(
+            JNIEnv * env, jobject obj, jint fd, jint size);
+};
+
+JNIEXPORT jint JNICALL Java_android_util_MemoryIntArrayTest_nativeCreateAshmem(
+        __attribute__((unused)) JNIEnv * env,__attribute__((unused)) jobject obj,
+        jstring name, jint size)
+{
+    return android_util_MemoryIntArrayTest_createAshmem(env, obj, name, size);
+}
+
+JNIEXPORT void JNICALL Java_android_util_MemoryIntArrayTest_nativeSetAshmemSize(
+        __attribute__((unused)) JNIEnv * env,__attribute__((unused)) jobject obj,
+        jint fd, jint size)
+{
+    android_util_MemoryIntArrayTest_setAshmemSize(env, obj, fd, size);
+}

core/tests/utiltests/src/android/util/IRemoteMemoryIntArray.aidl

@@ -20,11 +20,12 @@ import android.util.MemoryIntArray;
 
 interface IRemoteMemoryIntArray {
     MemoryIntArray peekInstance();
-    void create(int size, boolean clientWritable);
+    void create(int size);
     boolean isWritable();
     int get(int index);
     void set(int index, int value);
     int size();
     void close();
     boolean isClosed();
+    void accessLastElementInRemoteProcess(in MemoryIntArray array);
 }

core/tests/utiltests/src/android/util/MemoryIntArrayTest.java

@@ -28,14 +28,22 @@ import libcore.io.IoUtils;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
+import java.lang.reflect.Field;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
 @RunWith(AndroidJUnit4.class)
 public class MemoryIntArrayTest {
+    static {
+        System.loadLibrary("cutils");
+        System.loadLibrary("memoryintarraytest");
+    }
 
     @Test
     public void testSize() throws Exception {
         MemoryIntArray array = null;
         try {
-            array = new MemoryIntArray(3, false);
+            array = new MemoryIntArray(3);
             assertEquals("size must be three", 3, array.size());
         } finally {
             IoUtils.closeQuietly(array);
@@ -46,7 +54,7 @@ public class MemoryIntArrayTest {
     public void testGetSet() throws Exception {
         MemoryIntArray array = null;
         try {
-            array = new MemoryIntArray(3, false);
+            array = new MemoryIntArray(3);
 
             array.set(0, 1);
             array.set(1, 2);
@@ -64,7 +72,7 @@ public class MemoryIntArrayTest {
     public void testWritable() throws Exception {
         MemoryIntArray array = null;
         try {
-            array = new MemoryIntArray(3, true);
+            array = new MemoryIntArray(3);
             assertTrue("Must be mutable", array.isWritable());
         } finally {
             IoUtils.closeQuietly(array);
@@ -75,7 +83,7 @@ public class MemoryIntArrayTest {
     public void testClose() throws Exception {
         MemoryIntArray array = null;
         try {
-            array = new MemoryIntArray(3, false);
+            array = new MemoryIntArray(3);
             array.close();
             assertTrue("Must be closed", array.isClosed());
         } finally {
@@ -90,7 +98,7 @@ public class MemoryIntArrayTest {
         MemoryIntArray firstArray = null;
         MemoryIntArray secondArray = null;
         try {
-            firstArray = new MemoryIntArray(3, false);
+            firstArray = new MemoryIntArray(3);
 
             firstArray.set(0, 1);
             firstArray.set(1, 2);
@@ -117,7 +125,7 @@ public class MemoryIntArrayTest {
     public void testInteractOnceClosed() throws Exception {
         MemoryIntArray array = null;
         try {
-            array = new MemoryIntArray(3, false);
+            array = new MemoryIntArray(3);
             array.close();
 
             array.close();
@@ -160,7 +168,7 @@ public class MemoryIntArrayTest {
     public void testInteractPutOfBounds() throws Exception {
         MemoryIntArray array = null;
         try {
-            array = new MemoryIntArray(3, false);
+            array = new MemoryIntArray(3);
 
             try {
                 array.get(-1);
@@ -198,7 +206,7 @@ public class MemoryIntArrayTest {
     public void testOverMaxSize() throws Exception {
         MemoryIntArray array = null;
         try {
-            array = new MemoryIntArray(MemoryIntArray.getMaxSize() + 1, false);
+            array = new MemoryIntArray(MemoryIntArray.getMaxSize() + 1);
             fail("Cannot use over max size");
         } catch (IllegalArgumentException e) {
             /* expected */
@@ -209,7 +217,7 @@ public class MemoryIntArrayTest {
 
     @Test
     public void testNotMutableByUnprivilegedClients() throws Exception {
-        RemoteIntArray remoteIntArray = new RemoteIntArray(1, false);
+        RemoteIntArray remoteIntArray = new RemoteIntArray(1);
         try {
             assertNotNull("Couldn't get remote instance", remoteIntArray);
             MemoryIntArray localIntArray = remoteIntArray.peekInstance();
@@ -230,4 +238,64 @@ public class MemoryIntArrayTest {
             remoteIntArray.destroy();
         }
     }
+
+    @Test
+    public void testAshmemSizeMatchesMemoryIntArraySize() throws Exception {
+        boolean success = false;
+
+        // Get a handle to a remote process to send the fd
+        RemoteIntArray remoteIntArray = new RemoteIntArray(1);
+        try {
+            // Let us try 100 times
+            for (int i = 0; i < 100; i++) {
+                // Create a MemoryIntArray to muck with
+                MemoryIntArray array = new MemoryIntArray(1);
+
+                // Create the fd to stuff in the MemoryIntArray
+                final int fd = nativeCreateAshmem("foo", 1);
+
+                // Replace the fd with our ahsmem region
+                Field fdFiled = MemoryIntArray.class.getDeclaredField("mFd");
+                fdFiled.setAccessible(true);
+                fdFiled.set(array, fd);
+
+                CountDownLatch countDownLatch = new CountDownLatch(2);
+
+                new Thread() {
+                    @Override
+                    public void run() {
+                        for (int i = 2; i < Integer.MAX_VALUE; i++) {
+                            if (countDownLatch.getCount() == 1) {
+                                countDownLatch.countDown();
+                                return;
+                            }
+                            nativeSetAshmemSize(fd, i);
+                        }
+                    }
+                }.start();
+
+                try {
+                    remoteIntArray.accessLastElementInRemoteProcess(array);
+                } catch (IllegalArgumentException e) {
+                    success = true;
+                }
+
+                countDownLatch.countDown();
+                countDownLatch.await(1000, TimeUnit.MILLISECONDS);
+
+                if (success) {
+                    break;
+                }
+            }
+        } finally {
+            remoteIntArray.destroy();
+        }
+
+        if (!success) {
+            fail("MemoryIntArray should catch ahshmem size changing under it");
+        }
+    }
+
+    private native int nativeCreateAshmem(String name, int size);
+    private native void nativeSetAshmemSize(int fd, int size);
 }

core/tests/utiltests/src/android/util/RemoteIntArray.java

@@ -40,7 +40,7 @@ final class RemoteIntArray implements ServiceConnection, Closeable {
 
     private android.util.IRemoteMemoryIntArray mRemoteInstance;
 
-    public RemoteIntArray(int size, boolean clientWritable) throws IOException, TimeoutException {
+    public RemoteIntArray(int size) throws IOException, TimeoutException {
         mIntent.setComponent(new ComponentName(InstrumentationRegistry.getContext(),
                 RemoteMemoryIntArrayService.class));
         synchronized (mLock) {
@@ -48,7 +48,7 @@ final class RemoteIntArray implements ServiceConnection, Closeable {
                 bindLocked();
             }
             try {
-                mRemoteInstance.create(size, clientWritable);
+                mRemoteInstance.create(size);
             } catch (RemoteException e) {
                 throw new IOException(e);
             }
@@ -148,6 +148,14 @@ final class RemoteIntArray implements ServiceConnection, Closeable {
         }
     }
 
+    public void accessLastElementInRemoteProcess(MemoryIntArray array) {
+        try {
+            mRemoteInstance.accessLastElementInRemoteProcess(array);
+        } catch (RemoteException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
     @Override
     public void onServiceConnected(ComponentName name, IBinder service) {
         synchronized (mLock) {

core/tests/utiltests/src/android/util/RemoteMemoryIntArrayService.java

@@ -35,10 +35,10 @@ public class RemoteMemoryIntArrayService extends Service {
         return new android.util.IRemoteMemoryIntArray.Stub() {
 
             @Override
-            public void create(int size, boolean clientWritable) {
+            public void create(int size) {
                 synchronized (mLock) {
                     try {
-                        mArray = new MemoryIntArray(size, clientWritable);
+                        mArray = new MemoryIntArray(size);
                     } catch (IOException e) {
                         throw new IllegalStateException(e);
                     }
@@ -109,6 +109,15 @@ public class RemoteMemoryIntArrayService extends Service {
                     return mArray.isClosed();
                 }
             }
+
+            @Override
+            public void accessLastElementInRemoteProcess(MemoryIntArray array) {
+                try {
+                    array.get(array.size() - 1);
+                } catch (IOException e) {
+                    throw new IllegalStateException(e);
+                }
+            }
         };
     }
 }

packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java

@@ -119,7 +119,7 @@ final class GenerationRegistry {
             // and twice max user count for system and secure.
             final int size = 1 + 2 + 10 + 2 * UserManager.getMaxSupportedUsers();
             try {
-                mBackingStore = new MemoryIntArray(size, false);
+                mBackingStore = new MemoryIntArray(size);
             } catch (IOException e) {
                 Slog.e(LOG_TAG, "Error creating generation tracker", e);
             }