diff --git a/Android.bp b/Android.bp
index d976b91..00b4198 100644
--- a/Android.bp
+++ b/Android.bp
@@ -294,6 +294,7 @@
     srcs: [
         ":framework-non-updatable-sources",
         "core/java/**/*.logtags",
+        ":apex-info-list",
     ],
     aidl: {
         generate_get_transaction_name: true,
diff --git a/core/java/com/android/internal/content/om/OverlayConfig.java b/core/java/com/android/internal/content/om/OverlayConfig.java
index 3f3c9bd..7c39118 100644
--- a/core/java/com/android/internal/content/om/OverlayConfig.java
+++ b/core/java/com/android/internal/content/om/OverlayConfig.java
@@ -25,17 +25,22 @@
 import android.util.ArrayMap;
 import android.util.Log;
 
+import com.android.apex.ApexInfo;
+import com.android.apex.XmlParser;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.content.om.OverlayConfigParser.OverlayPartition;
 import com.android.internal.content.om.OverlayConfigParser.ParsedConfiguration;
 import com.android.internal.content.om.OverlayScanner.ParsedOverlayInfo;
 import com.android.internal.util.Preconditions;
+import com.android.internal.util.function.TriConsumer;
 
 import java.io.File;
+import java.io.FileInputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Comparator;
-import java.util.function.BiConsumer;
+import java.util.List;
 import java.util.function.Supplier;
 
 /**
@@ -73,7 +78,7 @@
     public interface PackageProvider {
 
         /** Performs the given action for each package. */
-        void forEachPackage(BiConsumer<ParsingPackageRead, Boolean> p);
+        void forEachPackage(TriConsumer<ParsingPackageRead, Boolean, File> p);
     }
 
     private static final Comparator<ParsedConfiguration> sStaticOverlayComparator = (c1, c2) -> {
@@ -115,6 +120,8 @@
                             p)));
         }
 
+        ArrayMap<Integer, List<String>> activeApexesPerPartition = getActiveApexes(partitions);
+
         boolean foundConfigFile = false;
         ArrayList<ParsedOverlayInfo> packageManagerOverlayInfos = null;
 
@@ -123,7 +130,9 @@
             final OverlayPartition partition = partitions.get(i);
             final OverlayScanner scanner = (scannerFactory == null) ? null : scannerFactory.get();
             final ArrayList<ParsedConfiguration> partitionOverlays =
-                    OverlayConfigParser.getConfigurations(partition, scanner);
+                    OverlayConfigParser.getConfigurations(partition, scanner,
+                            activeApexesPerPartition.getOrDefault(partition.type,
+                                    Collections.emptyList()));
             if (partitionOverlays != null) {
                 foundConfigFile = true;
                 overlays.addAll(partitionOverlays);
@@ -145,7 +154,8 @@
                 // Filter out overlays not present in the partition.
                 partitionOverlayInfos = new ArrayList<>(packageManagerOverlayInfos);
                 for (int j = partitionOverlayInfos.size() - 1; j >= 0; j--) {
-                    if (!partition.containsFile(partitionOverlayInfos.get(j).path)) {
+                    if (!partition.containsFile(partitionOverlayInfos.get(j)
+                            .getOriginalPartitionPath())) {
                         partitionOverlayInfos.remove(j);
                     }
                 }
@@ -292,16 +302,49 @@
     private static ArrayList<ParsedOverlayInfo> getOverlayPackageInfos(
             @NonNull PackageProvider packageManager) {
         final ArrayList<ParsedOverlayInfo> overlays = new ArrayList<>();
-        packageManager.forEachPackage((ParsingPackageRead p, Boolean isSystem) -> {
+        packageManager.forEachPackage((ParsingPackageRead p, Boolean isSystem,
+                @Nullable File preInstalledApexPath) -> {
             if (p.getOverlayTarget() != null && isSystem) {
                 overlays.add(new ParsedOverlayInfo(p.getPackageName(), p.getOverlayTarget(),
                         p.getTargetSdkVersion(), p.isOverlayIsStatic(), p.getOverlayPriority(),
-                        new File(p.getBaseApkPath())));
+                        new File(p.getBaseApkPath()), preInstalledApexPath));
             }
         });
         return overlays;
     }
 
+    /** Returns a map of PartitionType to List of active APEX module names. */
+    @NonNull
+    private static ArrayMap<Integer, List<String>> getActiveApexes(
+            @NonNull List<OverlayPartition> partitions) {
+        // An Overlay in an APEX, which is an update of an APEX in a given partition,
+        // is considered as belonging to that partition.
+        ArrayMap<Integer, List<String>> result = new ArrayMap<>();
+        for (OverlayPartition partition : partitions) {
+            result.put(partition.type, new ArrayList<String>());
+        }
+        // Read from apex-info-list because ApexManager is not accessible to zygote.
+        File apexInfoList = new File("/apex/apex-info-list.xml");
+        if (apexInfoList.exists() && apexInfoList.canRead()) {
+            try (FileInputStream stream = new FileInputStream(apexInfoList)) {
+                List<ApexInfo> apexInfos = XmlParser.readApexInfoList(stream).getApexInfo();
+                for (ApexInfo info : apexInfos) {
+                    if (info.getIsActive()) {
+                        for (OverlayPartition partition : partitions) {
+                            if (partition.containsPath(info.getPreinstalledModulePath())) {
+                                result.get(partition.type).add(info.getModuleName());
+                                break;
+                            }
+                        }
+                    }
+                }
+            } catch (Exception e) {
+                Log.w(TAG, "Error reading apex-info-list: " + e);
+            }
+        }
+        return result;
+    }
+
     /** Represents a single call to idmap create-multiple. */
     @VisibleForTesting
     public static class IdmapInvocation {
diff --git a/core/java/com/android/internal/content/om/OverlayConfigParser.java b/core/java/com/android/internal/content/om/OverlayConfigParser.java
index a86e595..d48c2e7 100644
--- a/core/java/com/android/internal/content/om/OverlayConfigParser.java
+++ b/core/java/com/android/internal/content/om/OverlayConfigParser.java
@@ -40,6 +40,7 @@
 import java.io.FileReader;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.List;
 
 /**
  * Responsible for parsing configurations of Runtime Resource Overlays that control mutability,
@@ -192,13 +193,19 @@
      */
     @Nullable
     static ArrayList<ParsedConfiguration> getConfigurations(
-            @NonNull OverlayPartition partition, @Nullable OverlayScanner scanner) {
-        if (partition.getOverlayFolder() == null) {
-            return null;
+            @NonNull OverlayPartition partition, @Nullable OverlayScanner scanner,
+            @NonNull List<String> activeApexes) {
+        if (scanner != null) {
+            if (partition.getOverlayFolder() != null) {
+                scanner.scanDir(partition.getOverlayFolder());
+            }
+            for (String apex : activeApexes) {
+                scanner.scanDir(new File("/apex/" + apex + "/overlay/"));
+            }
         }
 
-        if (scanner != null) {
-            scanner.scanDir(partition.getOverlayFolder());
+        if (partition.getOverlayFolder() == null) {
+            return null;
         }
 
         final File configFile = new File(partition.getOverlayFolder(), CONFIG_DEFAULT_FILENAME);
diff --git a/core/java/com/android/internal/content/om/OverlayScanner.java b/core/java/com/android/internal/content/om/OverlayScanner.java
index 6b5cb8d..138d1ce 100644
--- a/core/java/com/android/internal/content/om/OverlayScanner.java
+++ b/core/java/com/android/internal/content/om/OverlayScanner.java
@@ -47,23 +47,38 @@
         public final boolean isStatic;
         public final int priority;
         public final File path;
+        @Nullable public final File preInstalledApexPath;
 
         public ParsedOverlayInfo(String packageName, String targetPackageName,
-                int targetSdkVersion, boolean isStatic, int priority, File path) {
+                int targetSdkVersion, boolean isStatic, int priority, File path,
+                @Nullable File preInstalledApexPath) {
             this.packageName = packageName;
             this.targetPackageName = targetPackageName;
             this.targetSdkVersion = targetSdkVersion;
             this.isStatic = isStatic;
             this.priority = priority;
             this.path = path;
+            this.preInstalledApexPath = preInstalledApexPath;
         }
 
         @Override
         public String toString() {
             return getClass().getSimpleName() + String.format("{packageName=%s"
                             + ", targetPackageName=%s, targetSdkVersion=%s, isStatic=%s"
-                            + ", priority=%s, path=%s}",
-                    packageName, targetPackageName, targetSdkVersion, isStatic, priority, path);
+                            + ", priority=%s, path=%s, preInstalledApexPath=%s}",
+                    packageName, targetPackageName, targetSdkVersion, isStatic,
+                    priority, path, preInstalledApexPath);
+        }
+
+        /**
+         * Retrieves the path of the overlay in its original installation partition.
+         *
+         * An Overlay in an APEX, which is an update of an APEX in a given partition,
+         * is considered as belonging to that partition.
+         */
+        @NonNull
+        public File getOriginalPartitionPath() {
+            return preInstalledApexPath != null ? preInstalledApexPath : path;
         }
     }
 
@@ -138,6 +153,6 @@
         return apkLite.getTargetPackageName() == null ? null :
                 new ParsedOverlayInfo(apkLite.getPackageName(), apkLite.getTargetPackageName(),
                         apkLite.getTargetSdkVersion(), apkLite.isOverlayIsStatic(),
-                        apkLite.getOverlayPriority(), new File(apkLite.getPath()));
+                        apkLite.getOverlayPriority(), new File(apkLite.getPath()), null);
     }
 }
diff --git a/core/jni/fd_utils.cpp b/core/jni/fd_utils.cpp
index 6f5cc53..40f6e4f 100644
--- a/core/jni/fd_utils.cpp
+++ b/core/jni/fd_utils.cpp
@@ -138,6 +138,14 @@
         return true;
     }
 
+    // Allow Runtime Resource Overlays inside APEXes.
+    static const char* kOverlayPathSuffix = "/overlay";
+    if (android::base::StartsWith(path, kApexPrefix) &&
+        android::base::EndsWith(android::base::Dirname(path), kOverlayPathSuffix) &&
+        android::base::EndsWith(path, kApkSuffix) && path.find("/../") == std::string::npos) {
+        return true;
+    }
+
     static const char* kOverlayIdmapPrefix = "/data/resource-cache/";
     static const char* kOverlayIdmapSuffix = ".apk@idmap";
     if (android::base::StartsWith(path, kOverlayIdmapPrefix) &&
diff --git a/core/tests/coretests/src/com/android/internal/content/res/OverlayConfigIterationRule.java b/core/tests/coretests/src/com/android/internal/content/res/OverlayConfigIterationRule.java
index c50c818..e2c40d8 100644
--- a/core/tests/coretests/src/com/android/internal/content/res/OverlayConfigIterationRule.java
+++ b/core/tests/coretests/src/com/android/internal/content/res/OverlayConfigIterationRule.java
@@ -28,6 +28,7 @@
 import com.android.internal.content.om.OverlayConfig.PackageProvider;
 import com.android.internal.content.om.OverlayScanner;
 import com.android.internal.content.om.OverlayScanner.ParsedOverlayInfo;
+import com.android.internal.util.function.TriConsumer;
 
 import org.junit.Assert;
 import org.junit.rules.TestRule;
@@ -39,7 +40,6 @@
 import java.io.File;
 import java.io.IOException;
 import java.util.Map;
-import java.util.function.BiConsumer;
 import java.util.function.Supplier;
 
 /**
@@ -73,7 +73,7 @@
             final File canonicalPath = new File(path.getCanonicalPath());
             mOverlayStubResults.put(canonicalPath, new ParsedOverlayInfo(
                     packageName, targetPackage, targetSdkVersion, isStatic, priority,
-                    canonicalPath));
+                    canonicalPath, null));
         } catch (IOException e) {
             Assert.fail("Failed to add overlay " + e);
         }
@@ -135,8 +135,8 @@
                 mIteration = Iteration.SYSTEM_SERVER;
                 doAnswer((InvocationOnMock invocation) -> {
                     final Object[] args = invocation.getArguments();
-                    final BiConsumer<ParsingPackageRead, Boolean> f =
-                            (BiConsumer<ParsingPackageRead, Boolean>) args[0];
+                    final TriConsumer<ParsingPackageRead, Boolean, File> f =
+                            (TriConsumer<ParsingPackageRead, Boolean, File>) args[0];
                     for (Map.Entry<File, ParsedOverlayInfo> overlay :
                             mOverlayStubResults.entrySet()) {
                         final ParsingPackageRead a = Mockito.mock(ParsingPackageRead.class);
@@ -147,7 +147,8 @@
                         when(a.isOverlayIsStatic()).thenReturn(info.isStatic);
                         when(a.getOverlayPriority()).thenReturn(info.priority);
                         when(a.getBaseApkPath()).thenReturn(info.path.getPath());
-                        f.accept(a, !info.path.getPath().contains("data/overlay"));
+                        f.accept(a, !info.path.getPath().contains("data/overlay"),
+                                /*preInstalledApexPath=*/null);
                     }
                     return null;
                 }).when(mPkgProvider).forEachPackage(any());
diff --git a/services/core/java/com/android/server/pm/PackageManagerService.java b/services/core/java/com/android/server/pm/PackageManagerService.java
index f6acad0..827dfc0 100644
--- a/services/core/java/com/android/server/pm/PackageManagerService.java
+++ b/services/core/java/com/android/server/pm/PackageManagerService.java
@@ -7337,9 +7337,16 @@
 
             // Parse overlay configuration files to set default enable state, mutability, and
             // priority of system overlays.
+            final ArrayMap<String, File> apkInApexPreInstalledPaths = new ArrayMap<>();
+            for (ApexManager.ActiveApexInfo apexInfo : mApexManager.getActiveApexInfos()) {
+                for (String packageName : mApexManager.getApksInApex(apexInfo.apexModuleName)) {
+                    apkInApexPreInstalledPaths.put(packageName, apexInfo.preInstalledApexPath);
+                }
+            }
             mOverlayConfig = OverlayConfig.initializeSystemInstance(
                     consumer -> mPmInternal.forEachPackage(
-                            pkg -> consumer.accept(pkg, pkg.isSystem())));
+                            pkg -> consumer.accept(pkg, pkg.isSystem(),
+                              apkInApexPreInstalledPaths.get(pkg.getPackageName()))));
 
             // Prune any system packages that no longer exist.
             final List<String> possiblyDeletedUpdatedSystemApps = new ArrayList<>();