Revert "Fix vulnerability in MemoryIntArray" am: 1f06508bc6 am: 64b5725900 am: 60357eb6bd
am: 590b77da13
Change-Id: Ida195bcbaf3c3fad184865938dfff9f475879c16
diff --git a/core/java/android/util/MemoryIntArray.java b/core/java/android/util/MemoryIntArray.java
index 0d62054..83e693c 100644
--- a/core/java/android/util/MemoryIntArray.java
+++ b/core/java/android/util/MemoryIntArray.java
@@ -35,13 +35,13 @@
* 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.
- * The owner process is the process that created the array. The shared
- * memory is pinned (not reclaimed by the system) until the owning process
- * dies or the data structure is closed. This class is <strong>not</strong>
- * thread safe. You should not interact with an instance of this class
- * once it is closed. If you pass back to the owner process an instance
- * it will be read only even in the owning process.
+ * read/write. There may be multiple client processes that can only read or
+ * read/write depending how the data structure was configured when
+ * instantiated. The owner process is the process that created the array.
+ * The shared memory is pinned (not reclaimed by the system) until the
+ * owning process dies or the data structure is closed. This class
+ * is <strong>not</strong> thread safe. You should not interact with
+ * an instance of this class once it is closed.
* </p>
*
* @hide
@@ -51,7 +51,8 @@
private static final int MAX_SIZE = 1024;
- private final boolean mIsOwner;
+ private final int mOwnerPid;
+ private final boolean mClientWritable;
private final long mMemoryAddr;
private int mFd;
@@ -63,24 +64,31 @@
* @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) throws IOException {
+ public MemoryIntArray(int size, boolean clientWritable) throws IOException {
if (size > MAX_SIZE) {
throw new IllegalArgumentException("Max size is " + MAX_SIZE);
}
- mIsOwner = true;
+ mOwnerPid = Process.myPid();
+ mClientWritable = clientWritable;
final String name = UUID.randomUUID().toString();
mFd = nativeCreate(name, size);
- mMemoryAddr = nativeOpen(mFd, mIsOwner);
+ mMemoryAddr = nativeOpen(mFd, true, clientWritable);
}
private MemoryIntArray(Parcel parcel) throws IOException {
- mIsOwner = false;
+ mOwnerPid = parcel.readInt();
+ mClientWritable = (parcel.readInt() == 1);
ParcelFileDescriptor pfd = parcel.readParcelable(null);
if (pfd == null) {
throw new IOException("No backing file descriptor");
}
mFd = pfd.detachFd();
- mMemoryAddr = nativeOpen(mFd, mIsOwner);
+ final long memoryAddress = parcel.readLong();
+ if (isOwner()) {
+ mMemoryAddr = memoryAddress;
+ } else {
+ mMemoryAddr = nativeOpen(mFd, false, mClientWritable);
+ }
}
/**
@@ -88,7 +96,7 @@
*/
public boolean isWritable() {
enforceNotClosed();
- return mIsOwner;
+ return isOwner() || mClientWritable;
}
/**
@@ -101,7 +109,7 @@
public int get(int index) throws IOException {
enforceNotClosed();
enforceValidIndex(index);
- return nativeGet(mFd, mMemoryAddr, index);
+ return nativeGet(mFd, mMemoryAddr, index, isOwner());
}
/**
@@ -117,7 +125,7 @@
enforceNotClosed();
enforceWritable();
enforceValidIndex(index);
- nativeSet(mFd, mMemoryAddr, index, value);
+ nativeSet(mFd, mMemoryAddr, index, value, isOwner());
}
/**
@@ -138,7 +146,7 @@
@Override
public void close() throws IOException {
if (!isClosed()) {
- nativeClose(mFd, mMemoryAddr, mIsOwner);
+ nativeClose(mFd, mMemoryAddr, isOwner());
mFd = -1;
}
}
@@ -165,7 +173,10 @@
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();
}
@@ -191,6 +202,10 @@
return mFd;
}
+ private boolean isOwner() {
+ return mOwnerPid == Process.myPid();
+ }
+
private void enforceNotClosed() {
if (isClosed()) {
throw new IllegalStateException("cannot interact with a closed instance");
@@ -212,10 +227,10 @@
}
private native int nativeCreate(String name, int size);
- private native long nativeOpen(int fd, boolean owner);
+ private native long nativeOpen(int fd, boolean owner, boolean writable);
private native void nativeClose(int fd, long memoryAddr, boolean owner);
- private native int nativeGet(int fd, long memoryAddr, int index);
- private native void nativeSet(int fd, long memoryAddr, int index, int value);
+ private native int nativeGet(int fd, long memoryAddr, int index, boolean owner);
+ private native void nativeSet(int fd, long memoryAddr, int index, int value, boolean owner);
private native int nativeSize(int fd);
/**
@@ -232,7 +247,8 @@
try {
return new MemoryIntArray(parcel);
} catch (IOException ioe) {
- throw new IllegalArgumentException("Error unparceling MemoryIntArray");
+ Log.e(TAG, "Error unparceling MemoryIntArray");
+ return null;
}
}
diff --git a/core/jni/android_util_MemoryIntArray.cpp b/core/jni/android_util_MemoryIntArray.cpp
index a8e1452..d0c0f2f 100644
--- a/core/jni/android_util_MemoryIntArray.cpp
+++ b/core/jni/android_util_MemoryIntArray.cpp
@@ -54,7 +54,7 @@
}
static jlong android_util_MemoryIntArray_open(JNIEnv* env, jobject clazz, jint fd,
- jboolean owner)
+ jboolean owner, jboolean writable)
{
if (fd < 0) {
jniThrowException(env, "java/io/IOException", "bad file descriptor");
@@ -67,35 +67,19 @@
return -1;
}
- // 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;
+ int protMode = (owner || writable) ? (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) {
+ if (owner && !writable) {
int setProtResult = ashmem_set_prot_region(fd, PROT_READ);
if (setProtResult < 0) {
jniThrowException(env, "java/io/IOException", "cannot set ashmem prot mode");
@@ -137,7 +121,7 @@
}
static jint android_util_MemoryIntArray_get(JNIEnv* env, jobject clazz,
- jint fd, jlong address, jint index)
+ jint fd, jlong address, jint index, jboolean owner)
{
if (fd < 0) {
jniThrowException(env, "java/io/IOException", "bad file descriptor");
@@ -154,7 +138,7 @@
}
static void android_util_MemoryIntArray_set(JNIEnv* env, jobject clazz,
- jint fd, jlong address, jint index, jint newValue)
+ jint fd, jlong address, jint index, jint newValue, jboolean owner)
{
if (fd < 0) {
jniThrowException(env, "java/io/IOException", "bad file descriptor");
@@ -187,10 +171,10 @@
static const JNINativeMethod methods[] = {
{"nativeCreate", "(Ljava/lang/String;I)I", (void*)android_util_MemoryIntArray_create},
- {"nativeOpen", "(IZ)J", (void*)android_util_MemoryIntArray_open},
+ {"nativeOpen", "(IZZ)J", (void*)android_util_MemoryIntArray_open},
{"nativeClose", "(IJZ)V", (void*)android_util_MemoryIntArray_close},
- {"nativeGet", "(IJI)I", (void*)android_util_MemoryIntArray_get},
- {"nativeSet", "(IJII)V", (void*) android_util_MemoryIntArray_set},
+ {"nativeGet", "(IJIZ)I", (void*)android_util_MemoryIntArray_get},
+ {"nativeSet", "(IJIIZ)V", (void*) android_util_MemoryIntArray_set},
{"nativeSize", "(I)I", (void*) android_util_MemoryIntArray_size},
};
diff --git a/core/tests/utiltests/Android.mk b/core/tests/utiltests/Android.mk
index d4a6493..6d1ebb4 100644
--- a/core/tests/utiltests/Android.mk
+++ b/core/tests/utiltests/Android.mk
@@ -12,8 +12,6 @@
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
diff --git a/core/tests/utiltests/jni/Android.bp b/core/tests/utiltests/jni/Android.bp
deleted file mode 100644
index e9a4144..0000000
--- a/core/tests/utiltests/jni/Android.bp
+++ /dev/null
@@ -1,27 +0,0 @@
-// 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.
-
-cc_library_shared {
- name: "libmemoryintarraytest",
- shared_libs: [
- "libcutils",
- ],
- clang: true,
- stl: "libc++",
- srcs: [
- "registration.cpp",
- "android_util_MemoryIntArrayTest.cpp",
- ],
- cflags: ["-Werror"],
-}
\ No newline at end of file
diff --git a/core/tests/utiltests/jni/android_util_MemoryIntArrayTest.cpp b/core/tests/utiltests/jni/android_util_MemoryIntArrayTest.cpp
deleted file mode 100644
index 57ee2d5..0000000
--- a/core/tests/utiltests/jni/android_util_MemoryIntArrayTest.cpp
+++ /dev/null
@@ -1,66 +0,0 @@
-/*
- * 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);
-}
diff --git a/core/tests/utiltests/jni/registration.cpp b/core/tests/utiltests/jni/registration.cpp
deleted file mode 100644
index 0c84d98..0000000
--- a/core/tests/utiltests/jni/registration.cpp
+++ /dev/null
@@ -1,43 +0,0 @@
-/*
- * 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);
-}
diff --git a/core/tests/utiltests/src/android/util/IRemoteMemoryIntArray.aidl b/core/tests/utiltests/src/android/util/IRemoteMemoryIntArray.aidl
index 10d14f1..0a65fff2 100644
--- a/core/tests/utiltests/src/android/util/IRemoteMemoryIntArray.aidl
+++ b/core/tests/utiltests/src/android/util/IRemoteMemoryIntArray.aidl
@@ -20,12 +20,11 @@
interface IRemoteMemoryIntArray {
MemoryIntArray peekInstance();
- void create(int size);
+ void create(int size, boolean clientWritable);
boolean isWritable();
int get(int index);
void set(int index, int value);
int size();
void close();
boolean isClosed();
- void accessLastElementInRemoteProcess(in MemoryIntArray array);
}
diff --git a/core/tests/utiltests/src/android/util/MemoryIntArrayTest.java b/core/tests/utiltests/src/android/util/MemoryIntArrayTest.java
index 85817bb..129e6b7 100644
--- a/core/tests/utiltests/src/android/util/MemoryIntArrayTest.java
+++ b/core/tests/utiltests/src/android/util/MemoryIntArrayTest.java
@@ -28,22 +28,14 @@
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);
+ array = new MemoryIntArray(3, false);
assertEquals("size must be three", 3, array.size());
} finally {
IoUtils.closeQuietly(array);
@@ -54,7 +46,7 @@
public void testGetSet() throws Exception {
MemoryIntArray array = null;
try {
- array = new MemoryIntArray(3);
+ array = new MemoryIntArray(3, false);
array.set(0, 1);
array.set(1, 2);
@@ -72,7 +64,7 @@
public void testWritable() throws Exception {
MemoryIntArray array = null;
try {
- array = new MemoryIntArray(3);
+ array = new MemoryIntArray(3, true);
assertTrue("Must be mutable", array.isWritable());
} finally {
IoUtils.closeQuietly(array);
@@ -83,7 +75,7 @@
public void testClose() throws Exception {
MemoryIntArray array = null;
try {
- array = new MemoryIntArray(3);
+ array = new MemoryIntArray(3, false);
array.close();
assertTrue("Must be closed", array.isClosed());
} finally {
@@ -98,7 +90,7 @@
MemoryIntArray firstArray = null;
MemoryIntArray secondArray = null;
try {
- firstArray = new MemoryIntArray(3);
+ firstArray = new MemoryIntArray(3, false);
firstArray.set(0, 1);
firstArray.set(1, 2);
@@ -125,7 +117,7 @@
public void testInteractOnceClosed() throws Exception {
MemoryIntArray array = null;
try {
- array = new MemoryIntArray(3);
+ array = new MemoryIntArray(3, false);
array.close();
array.close();
@@ -168,7 +160,7 @@
public void testInteractPutOfBounds() throws Exception {
MemoryIntArray array = null;
try {
- array = new MemoryIntArray(3);
+ array = new MemoryIntArray(3, false);
try {
array.get(-1);
@@ -206,7 +198,7 @@
public void testOverMaxSize() throws Exception {
MemoryIntArray array = null;
try {
- array = new MemoryIntArray(MemoryIntArray.getMaxSize() + 1);
+ array = new MemoryIntArray(MemoryIntArray.getMaxSize() + 1, false);
fail("Cannot use over max size");
} catch (IllegalArgumentException e) {
/* expected */
@@ -217,7 +209,7 @@
@Test
public void testNotMutableByUnprivilegedClients() throws Exception {
- RemoteIntArray remoteIntArray = new RemoteIntArray(1);
+ RemoteIntArray remoteIntArray = new RemoteIntArray(1, false);
try {
assertNotNull("Couldn't get remote instance", remoteIntArray);
MemoryIntArray localIntArray = remoteIntArray.peekInstance();
@@ -238,64 +230,4 @@
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);
}
diff --git a/core/tests/utiltests/src/android/util/RemoteIntArray.java b/core/tests/utiltests/src/android/util/RemoteIntArray.java
index 7dc3400..10c325f 100644
--- a/core/tests/utiltests/src/android/util/RemoteIntArray.java
+++ b/core/tests/utiltests/src/android/util/RemoteIntArray.java
@@ -40,7 +40,7 @@
private android.util.IRemoteMemoryIntArray mRemoteInstance;
- public RemoteIntArray(int size) throws IOException, TimeoutException {
+ public RemoteIntArray(int size, boolean clientWritable) throws IOException, TimeoutException {
mIntent.setComponent(new ComponentName(InstrumentationRegistry.getContext(),
RemoteMemoryIntArrayService.class));
synchronized (mLock) {
@@ -48,7 +48,7 @@
bindLocked();
}
try {
- mRemoteInstance.create(size);
+ mRemoteInstance.create(size, clientWritable);
} catch (RemoteException e) {
throw new IOException(e);
}
@@ -148,14 +148,6 @@
}
}
- 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) {
diff --git a/core/tests/utiltests/src/android/util/RemoteMemoryIntArrayService.java b/core/tests/utiltests/src/android/util/RemoteMemoryIntArrayService.java
index 9264c6c..35ae9a7 100644
--- a/core/tests/utiltests/src/android/util/RemoteMemoryIntArrayService.java
+++ b/core/tests/utiltests/src/android/util/RemoteMemoryIntArrayService.java
@@ -35,10 +35,10 @@
return new android.util.IRemoteMemoryIntArray.Stub() {
@Override
- public void create(int size) {
+ public void create(int size, boolean clientWritable) {
synchronized (mLock) {
try {
- mArray = new MemoryIntArray(size);
+ mArray = new MemoryIntArray(size, clientWritable);
} catch (IOException e) {
throw new IllegalStateException(e);
}
@@ -109,15 +109,6 @@
return mArray.isClosed();
}
}
-
- @Override
- public void accessLastElementInRemoteProcess(MemoryIntArray array) {
- try {
- array.get(array.size() - 1);
- } catch (IOException e) {
- throw new IllegalStateException(e);
- }
- }
};
}
}
diff --git a/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java b/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
index 6e291c7..f4f7986 100644
--- a/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
+++ b/packages/SettingsProvider/src/com/android/providers/settings/GenerationRegistry.java
@@ -119,7 +119,7 @@
// and twice max user count for system and secure.
final int size = 1 + 2 + 10 + 2 * UserManager.getMaxSupportedUsers();
try {
- mBackingStore = new MemoryIntArray(size);
+ mBackingStore = new MemoryIntArray(size, false);
} catch (IOException e) {
Slog.e(LOG_TAG, "Error creating generation tracker", e);
}