Access to all users' external storage.

System services holding this permission have external storage bound
one level higher, giving them access to all users' files.

Bug: 7003520
Change-Id: Ib2bcb8455740c713ebd01f71c9a2b89b4e642832

Author: jsharkey

core/java/android/os/Process.java

@@ -584,6 +584,8 @@ private static ProcessStartResult startViaZygote(final String processClass,
             }
             if (mountExternal == Zygote.MOUNT_EXTERNAL_MULTIUSER) {
                 argsForZygote.add("--mount-external-multiuser");
+            } else if (mountExternal == Zygote.MOUNT_EXTERNAL_MULTIUSER_ALL) {
+                argsForZygote.add("--mount-external-multiuser-all");
             }
             argsForZygote.add("--target-sdk-version=" + targetSdkVersion);
 

core/java/com/android/internal/os/ZygoteConnection.java

@@ -529,6 +529,8 @@ private void parseArgs(String args[])
                     niceName = arg.substring(arg.indexOf('=') + 1);
                 } else if (arg.equals("--mount-external-multiuser")) {
                     mountExternal = Zygote.MOUNT_EXTERNAL_MULTIUSER;
+                } else if (arg.equals("--mount-external-multiuser-all")) {
+                    mountExternal = Zygote.MOUNT_EXTERNAL_MULTIUSER_ALL;
                 } else {
                     break;
                 }

core/res/AndroidManifest.xml

@@ -725,6 +725,13 @@
         android:description="@string/permdesc_mediaStorageWrite"
         android:protectionLevel="signature|system" />
 
+    <!-- Allows an application to access all multi-user external storage @hide -->
+    <permission android:name="android.permission.ACCESS_ALL_EXTERNAL_STORAGE"
+        android:permissionGroup="android.permission-group.DEVELOPMENT_TOOLS"
+        android:label="@string/permlab_sdcardAccessAll"
+        android:description="@string/permdesc_sdcardAccessAll"
+        android:protectionLevel="signature" />
+
     <!-- ============================================ -->
     <!-- Permissions for low-level system interaction -->
     <!-- ============================================ -->

core/res/res/values/strings.xml

@@ -1616,6 +1616,11 @@
     <!-- Description of an application permission, listed so the user can choose whether they want to allow the application to do this. [CHAR LIMIT=NONE] -->
     <string name="permdesc_mediaStorageWrite" product="default">Allows the app to modify the contents of the internal media storage.</string>
 
+    <!-- Title of an application permission, listed so the user can choose whether they want to allow the application to do this. [CHAR LIMIT=30] -->
+    <string name="permlab_sdcardAccessAll">access external storage of all users</string>
+    <!-- Description of an application permission, listed so the user can choose whether they want to allow the application to do this. -->
+    <string name="permdesc_sdcardAccessAll">Allows the app to access external storage for all users.</string>
+
     <!-- Title of an application permission, listed so the user can choose whether they want to allow the application to do this. -->
     <string name="permlab_cache_filesystem">access the cache filesystem</string>
     <!-- Description of an application permission, listed so the user can choose whether they want to allow the application to do this. -->

services/java/com/android/server/am/ActivityManagerService.java

@@ -1991,13 +1991,19 @@ private final void startProcessLocked(ProcessRecord app,
                 try {
                     final PackageManager pm = mContext.getPackageManager();
                     gids = pm.getPackageGids(app.info.packageName);
+
+                    if (Environment.isExternalStorageEmulated()) {
+                        if (pm.checkPermission(
+                                android.Manifest.permission.ACCESS_ALL_EXTERNAL_STORAGE,
+                                app.info.packageName) == PERMISSION_GRANTED) {
+                            mountExternal = Zygote.MOUNT_EXTERNAL_MULTIUSER_ALL;
+                        } else {
+                            mountExternal = Zygote.MOUNT_EXTERNAL_MULTIUSER;
+                        }
+                    }
                 } catch (PackageManager.NameNotFoundException e) {
                     Slog.w(TAG, "Unable to retrieve gids", e);
                 }
-
-                if (Environment.isExternalStorageEmulated()) {
-                    mountExternal = Zygote.MOUNT_EXTERNAL_MULTIUSER;
-                }
             }
             if (mFactoryTest != SystemServer.FACTORY_TEST_OFF) {
                 if (mFactoryTest == SystemServer.FACTORY_TEST_LOW_LEVEL