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[RESTRICT AUTOMERGE] [SettingsProvider] mem limit should be checked before settings are updated

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Previously, a setting is updated before the memory usage limit
check, which can be exploited by malicious apps and cause OoM DoS.

This CL changes the logic to checkMemLimit -> update -> updateMemUsage.

BUG: 239415861
Test: atest com.android.providers.settings.SettingsStateTest

(cherry picked from commit 8eeb92950f)
Merged-In: I20551a2dba9aa79efa0c064824f349f551c2c2e4
Change-Id: I20551a2dba9aa79efa0c064824f349f551c2c2e4
This commit is contained in:
Songchun Fan
2022-08-17 09:37:18 -07:00
committed by Song Chun Fan
parent 822eef4399
commit f22267f8b2
2 changed files with 88 additions and 29 deletions
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79
packages/SettingsProvider/src/com/android/providers/settings/SettingsState.java
View File

@@ -384,9 +384,11 @@ final class SettingsState {
Setting newSetting = new Setting(name, oldSetting.getValue(), null,
oldSetting.getPackageName(), oldSetting.getTag(), false,
oldSetting.getId());
mSettings.put(name, newSetting);
updateMemoryUsagePerPackageLocked(newSetting.getPackageName(), oldValue,
int newSize = getNewMemoryUsagePerPackageLocked(newSetting.getPackageName(), oldValue,
newSetting.getValue(), oldDefaultValue, newSetting.getDefaultValue());
checkNewMemoryUsagePerPackageLocked(newSetting.getPackageName(), newSize);
mSettings.put(name, newSetting);
updateMemoryUsagePerPackageLocked(newSetting.getPackageName(), newSize);
scheduleWriteIfNeededLocked();
}
}
@@ -419,6 +421,12 @@ final class SettingsState {
Setting oldState = mSettings.get(name);
String oldValue = (oldState != null) ? oldState.value : null;
String oldDefaultValue = (oldState != null) ? oldState.defaultValue : null;
String newDefaultValue = makeDefault ? value : oldDefaultValue;
int newSize = getNewMemoryUsagePerPackageLocked(packageName, oldValue, value,
oldDefaultValue, newDefaultValue);
checkNewMemoryUsagePerPackageLocked(packageName, newSize);
Setting newState;
if (oldState != null) {
@@ -439,8 +447,7 @@ final class SettingsState {
addHistoricalOperationLocked(HISTORICAL_OPERATION_UPDATE, newState);
updateMemoryUsagePerPackageLocked(packageName, oldValue, value,
oldDefaultValue, newState.getDefaultValue());
updateMemoryUsagePerPackageLocked(packageName, newSize);
scheduleWriteIfNeededLocked();
@@ -558,13 +565,14 @@ final class SettingsState {
}
Setting oldState = mSettings.remove(name);
int newSize = getNewMemoryUsagePerPackageLocked(oldState.packageName, oldState.value,
null, oldState.defaultValue, null);
FrameworkStatsLog.write(FrameworkStatsLog.SETTING_CHANGED, name, /* value= */ "",
/* newValue= */ "", oldState.value, /* tag */ "", false, getUserIdFromKey(mKey),
FrameworkStatsLog.SETTING_CHANGED__REASON__DELETED);
updateMemoryUsagePerPackageLocked(oldState.packageName, oldState.value,
null, oldState.defaultValue, null);
updateMemoryUsagePerPackageLocked(oldState.packageName, newSize);
addHistoricalOperationLocked(HISTORICAL_OPERATION_DELETE, oldState);
@@ -585,16 +593,18 @@ final class SettingsState {
Setting oldSetting = new Setting(setting);
String oldValue = setting.getValue();
String oldDefaultValue = setting.getDefaultValue();
String newValue = oldDefaultValue;
String newDefaultValue = oldDefaultValue;
int newSize = getNewMemoryUsagePerPackageLocked(setting.packageName, oldValue,
newValue, oldDefaultValue, newDefaultValue);
checkNewMemoryUsagePerPackageLocked(setting.packageName, newSize);
if (!setting.reset()) {
return false;
}
String newValue = setting.getValue();
String newDefaultValue = setting.getDefaultValue();
updateMemoryUsagePerPackageLocked(setting.packageName, oldValue,
newValue, oldDefaultValue, newDefaultValue);
updateMemoryUsagePerPackageLocked(setting.packageName, newSize);
addHistoricalOperationLocked(HISTORICAL_OPERATION_RESET, oldSetting);
@@ -702,38 +712,49 @@ final class SettingsState {
}
@GuardedBy("mLock")
private void updateMemoryUsagePerPackageLocked(String packageName, String oldValue,
private boolean isExemptFromMemoryUsageCap(String packageName) {
return mMaxBytesPerAppPackage == MAX_BYTES_PER_APP_PACKAGE_UNLIMITED
|| SYSTEM_PACKAGE_NAME.equals(packageName);
}
@GuardedBy("mLock")
private void checkNewMemoryUsagePerPackageLocked(String packageName, int newSize)
throws IllegalStateException {
if (isExemptFromMemoryUsageCap(packageName)) {
return;
}
if (newSize > mMaxBytesPerAppPackage) {
throw new IllegalStateException("You are adding too many system settings. "
+ "You should stop using system settings for app specific data"
+ " package: " + packageName);
}
}
@GuardedBy("mLock")
private int getNewMemoryUsagePerPackageLocked(String packageName, String oldValue,
String newValue, String oldDefaultValue, String newDefaultValue) {
if (mMaxBytesPerAppPackage == MAX_BYTES_PER_APP_PACKAGE_UNLIMITED) {
return;
if (isExemptFromMemoryUsageCap(packageName)) {
return 0;
}
if (SYSTEM_PACKAGE_NAME.equals(packageName)) {
return;
}
final Integer currentSize = mPackageToMemoryUsage.get(packageName);
final int oldValueSize = (oldValue != null) ? oldValue.length() : 0;
final int newValueSize = (newValue != null) ? newValue.length() : 0;
final int oldDefaultValueSize = (oldDefaultValue != null) ? oldDefaultValue.length() : 0;
final int newDefaultValueSize = (newDefaultValue != null) ? newDefaultValue.length() : 0;
final int deltaSize = newValueSize + newDefaultValueSize
- oldValueSize - oldDefaultValueSize;
return Math.max((currentSize != null) ? currentSize + deltaSize : deltaSize, 0);
}
Integer currentSize = mPackageToMemoryUsage.get(packageName);
final int newSize = Math.max((currentSize != null)
? currentSize + deltaSize : deltaSize, 0);
if (newSize > mMaxBytesPerAppPackage) {
throw new IllegalStateException("You are adding too many system settings. "
+ "You should stop using system settings for app specific data"
+ " package: " + packageName);
@GuardedBy("mLock")
private void updateMemoryUsagePerPackageLocked(String packageName, int newSize) {
if (isExemptFromMemoryUsageCap(packageName)) {
return;
}
if (DEBUG) {
Slog.i(LOG_TAG, "Settings for package: " + packageName
+ " size: " + newSize + " bytes.");
}
mPackageToMemoryUsage.put(packageName, newSize);
}

38
packages/SettingsProvider/test/src/com/android/providers/settings/SettingsStateTest.java
View File

@@ -21,6 +21,8 @@ import android.util.Xml;
import org.xmlpull.v1.XmlSerializer;
import com.google.common.base.Strings;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
@@ -280,4 +282,40 @@ public class SettingsStateTest extends AndroidTestCase {
settingsState.setVersionLocked(SettingsState.SETTINGS_VERSION_NEW_ENCODING);
return settingsState;
}
public void testInsertSetting_memoryUsage() {
SettingsState settingsState = new SettingsState(getContext(), mLock, mSettingsFile, 1,
SettingsState.MAX_BYTES_PER_APP_PACKAGE_UNLIMITED, Looper.getMainLooper());
// No exception should be thrown when there is no cap
settingsState.insertSettingLocked(SETTING_NAME, Strings.repeat("A", 20001),
null, false, "p1");
settingsState.deleteSettingLocked(SETTING_NAME);
settingsState = new SettingsState(getContext(), mLock, mSettingsFile, 1,
SettingsState.MAX_BYTES_PER_APP_PACKAGE_LIMITED, Looper.getMainLooper());
// System package doesn't have memory usage limit
settingsState.insertSettingLocked(SETTING_NAME, Strings.repeat("A", 20001),
null, false, SYSTEM_PACKAGE);
settingsState.deleteSettingLocked(SETTING_NAME);
// Should not throw if usage is under the cap
settingsState.insertSettingLocked(SETTING_NAME, Strings.repeat("A", 19999),
null, false, "p1");
settingsState.deleteSettingLocked(SETTING_NAME);
try {
settingsState.insertSettingLocked(SETTING_NAME, Strings.repeat("A", 20001),
null, false, "p1");
fail("Should throw because it exceeded per package memory usage");
} catch (IllegalStateException ex) {
assertTrue(ex.getMessage().contains("p1"));
}
try {
settingsState.insertSettingLocked(SETTING_NAME, Strings.repeat("A", 20001),
null, false, "p1");
fail("Should throw because it exceeded per package memory usage");
} catch (IllegalStateException ex) {
assertTrue(ex.getMessage().contains("p1"));
}
assertTrue(settingsState.getSettingLocked(SETTING_NAME).isNull());
}
}