From 48d8d370f3d1dac06719ca6a52bda5f45a1a533a Mon Sep 17 00:00:00 2001
From: Riddle Hsu <riddlehsu@google.com>
Date: Wed, 19 Feb 2020 15:13:56 +0800
Subject: [PATCH] RESTRICT AUTOMERGE Create separated tasks for different apps
 from startActivities

Assume there are 2 applications A, B with different uids.
There are 4 activities A1, A2, B1, B2 with default task
affinity and launch mode.

After A1 called startActivities(B1, A2, B2):
 Original   : Task(A1, B1, A2, B2)
 This Change: Task(A1, B1), Task(A2, B2)
In other words, the source caller cannot launch its activity
above the activity of other application in the same task, and
it can still launch activity of other application in its task.

Bug: 145669109
Test: atest StartActivityTests# \
      testStartActivitiesWithDiffUidNotInSameTask
Change-Id: I97bd875146a52f62b8fe82235487ccefb2955e8e
---
 .../server/am/ActivityStartController.java    | 21 ++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/services/core/java/com/android/server/am/ActivityStartController.java b/services/core/java/com/android/server/am/ActivityStartController.java
index c926503da27dd..240f01d159a7b 100644
--- a/services/core/java/com/android/server/am/ActivityStartController.java
+++ b/services/core/java/com/android/server/am/ActivityStartController.java
@@ -334,6 +334,9 @@ public class ActivityStartController {
         } else {
             callingPid = callingUid = -1;
         }
+        boolean forceNewTask = false;
+        final int filterCallingUid = ActivityStarter.computeResolveFilterUid(
+                callingUid, realCallingUid, UserHandle.USER_NULL);
         final long origId = Binder.clearCallingIdentity();
         try {
             synchronized (mService) {
@@ -353,11 +356,13 @@ public class ActivityStartController {
 
                     // Don't modify the client's object!
                     intent = new Intent(intent);
+                    if (forceNewTask) {
+                        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+                    }
 
                     // Collect information about the target of the Intent.
                     ActivityInfo aInfo = mSupervisor.resolveActivity(intent, resolvedTypes[i], 0,
-                            null, userId, ActivityStarter.computeResolveFilterUid(
-                                    callingUid, realCallingUid, UserHandle.USER_NULL));
+                            null, userId, filterCallingUid);
                     // TODO: New, check if this is correct
                     aInfo = mService.getActivityInfoForUser(aInfo, userId);
 
@@ -397,7 +402,17 @@ public class ActivityStartController {
                         return res;
                     }
 
-                    resultTo = outActivity[0] != null ? outActivity[0].appToken : null;
+                    final ActivityRecord started = outActivity[0];
+                    if (started != null && started.getUid() == filterCallingUid) {
+                        // Only the started activity which has the same uid as the source caller can
+                        // be the caller of next activity.
+                        resultTo = started.appToken;
+                        forceNewTask = false;
+                    } else {
+                        // Different apps not adjacent to the caller are forced to be new task.
+                        resultTo = null;
+                        forceNewTask = true;
+                    }
                 }
             }
         } finally {