Fixed DPM.logoutUser() methods.

The initial implementation was setting the logout user to be SYSTEM
on non-headless system user mode, but recently it was changed to
return null if the user was not switched or started by the device
admin.

Test: atest com.android.cts.devicepolicy.DeviceOwnerTest#testCreateAndManageUser_LogoutUser_systemApi com.android.cts.devicepolicy.DeviceOwnerTest#testCreateAndManageUser_LogoutUser # on phones and automotive
Fixes: 216648012

Change-Id: I1f8f754167260a41df13dca13cb62467723c99b1

core/java/android/app/admin/DevicePolicyManager.java

@@ -10063,7 +10063,9 @@ public class DevicePolicyManager {
 
     /**
      * Called by a profile owner of secondary user that is affiliated with the device to stop the
-     * calling user and switch back to primary user.
+     * calling user and switch back to primary user (when the user was
+     * {@link #switchUser(ComponentName, UserHandle)} switched to) or stop the user (when it was
+     * {@link #startUserInBackground(ComponentName, UserHandle) started in background}.
      *
      * <p>Notice that on devices running with
      * {@link UserManager#isHeadlessSystemUserMode() headless system user mode}, there is no primary
@@ -10091,7 +10093,12 @@ public class DevicePolicyManager {
     }
 
     /**
-     * Same as {@link #logoutUser(ComponentName)}, but called by system (like Settings), not admin.
+     * Similar to {@link #logoutUser(ComponentName)}, except:
+     *
+     * <ul>
+     *   <li>Called by system (like Settings), not admin.
+     *   <li>It logs out the current user, not the caller.
+     * </ul>
      *
      * @hide
      */
@@ -10108,7 +10115,10 @@ public class DevicePolicyManager {
     }
     /**
      * Gets the user a {@link #logoutUser(ComponentName)} call would switch to,
-     * or {@code null} if the current user is not in a session.
+     * or {@code null} if the current user is not in a session (i.e., if it was not
+     * {@link #switchUser(ComponentName, UserHandle) switched} or
+     * {@link #startUserInBackground(ComponentName, UserHandle) started in background} by the
+     * device admin.
      *
      * @hide
      */

services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java

@@ -10907,7 +10907,7 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
                 if (mPendingUserCreatedCallbackTokens.contains(token)) {
                     // Ignore because it was triggered by createAndManageUser()
                     Slogf.d(LOG_TAG, "handleNewUserCreated(): ignoring for user " + userId
-                            + " due to token" + token);
+                            + " due to token " + token);
                     mPendingUserCreatedCallbackTokens.remove(token);
                     return;
                 }
@@ -11026,6 +11026,8 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
                 switched = mInjector.getIActivityManager().switchUser(userId);
                 if (!switched) {
                     Slogf.w(LOG_TAG, "Failed to switch to user %d", userId);
+                } else {
+                    Slogf.d(LOG_TAG, "Switched");
                 }
                 return switched;
             } catch (RemoteException e) {
@@ -11049,18 +11051,12 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
     }
 
     private @UserIdInt int getLogoutUserIdUnchecked() {
-        if (!mInjector.userManagerIsHeadlessSystemUserMode()) {
-            // mLogoutUserId is USER_SYSTEM as well, but there's no need to acquire the lock
-            return UserHandle.USER_SYSTEM;
-        }
         synchronized (getLockObject()) {
             return mLogoutUserId;
         }
     }
 
     private void clearLogoutUser() {
-        if (!mInjector.userManagerIsHeadlessSystemUserMode()) return; // ignore
-
         synchronized (getLockObject()) {
             setLogoutUserIdLocked(UserHandle.USER_NULL);
         }
@@ -11068,8 +11064,6 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
 
     @GuardedBy("getLockObject()")
     private void setLogoutUserIdLocked(@UserIdInt int userId) {
-        if (!mInjector.userManagerIsHeadlessSystemUserMode()) return; // ignore
-
         if (userId == UserHandle.USER_CURRENT) {
             userId = getCurrentForegroundUserId();
         }
@@ -11151,8 +11145,7 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
             return UserManager.USER_OPERATION_ERROR_MANAGED_PROFILE;
         }
 
-        // TODO(b/204585343): remove the headless system user check?
-        if (mInjector.userManagerIsHeadlessSystemUserMode() && callingUserId != mInjector
+        if (callingUserId != mInjector
                 .binderWithCleanCallingIdentity(() -> getCurrentForegroundUserId())) {
             Slogf.d(LOG_TAG, "logoutUser(): user %d is in background, just stopping, not switching",
                     callingUserId);
@@ -11168,8 +11161,15 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
         Preconditions.checkCallAuthorization(
                 canManageUsers(caller) || hasCallingOrSelfPermission(permission.CREATE_USERS));
 
-        int result = logoutUserUnchecked(getCurrentForegroundUserId());
-        Slogf.d(LOG_TAG, "logout called by uid %d. Result: %d", caller.getUid(), result);
+        int currentUserId = getCurrentForegroundUserId();
+        if (VERBOSE_LOG) {
+            Slogf.v(LOG_TAG, "logout() called by uid %d; current user is %d", caller.getUid(),
+                    currentUserId);
+        }
+        int result = logoutUserUnchecked(currentUserId);
+        if (VERBOSE_LOG) {
+            Slogf.v(LOG_TAG, "Result of logout(): %d", result);
+        }
         return result;
     }