From 2be3ba49733df585bcfbf63d3b299d15dbfb0f13 Mon Sep 17 00:00:00 2001
From: Riddle Hsu <riddlehsu@google.com>
Date: Sat, 22 Feb 2020 23:20:41 +0800
Subject: 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: run cts --test android.server.cts.StartActivityTests \
      -m CtsServicesHostTestCases
Change-Id: I97bd875146a52f62b8fe82235487ccefb2955e8e
---
 .../java/com/android/server/am/ActivityStarter.java     | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/services/core/java/com/android/server/am/ActivityStarter.java b/services/core/java/com/android/server/am/ActivityStarter.java
index 7ce80d33ed00..57a0756703d1 100644
--- a/services/core/java/com/android/server/am/ActivityStarter.java
+++ b/services/core/java/com/android/server/am/ActivityStarter.java
@@ -951,6 +951,8 @@ class ActivityStarter {
         } else {
             callingPid = callingUid = -1;
         }
+        boolean forceNewTask = false;
+        final int filterCallingUid = callingUid >= 0 ? callingUid : realCallingUid;
         final long origId = Binder.clearCallingIdentity();
         try {
             synchronized (mService) {
@@ -970,6 +972,9 @@ class ActivityStarter {
 
                     // 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,
@@ -995,7 +1000,17 @@ class ActivityStarter {
                         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 {
-- 
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