From 3ec9c56bd4ac40cf11f00866639b37a955eabc8b Mon Sep 17 00:00:00 2001
From: Jing Ji <jji@google.com>
Date: Tue, 25 Oct 2022 22:39:52 -0700
Subject: [PATCH] DO NOT MERGE: ActivityManager#killBackgroundProcesses can
 kill caller's own app only

unless it's a system app.

Bug: 239423414
Bug: 223376078
Test: atest CtsAppTestCases:ActivityManagerTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:d1c95670b248df945784b0f2830acf83b5682de3)
Merged-In: Iac6baa889965b8ffecd9a43179a4c96632ad1d02
AOSP-Change-Id: Iac6baa889965b8ffecd9a43179a4c96632ad1d02

Change-Id: I3a39b5e2b2ff0c314972ddeccb012894de704de8
---
 .../server/am/ActivityManagerService.java        | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 41b1ddaf887bb..bcb7276b4014e 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -4268,6 +4268,22 @@ void killAllBackgroundProcessesExcept(int minTargetSdk, int maxProcState) {
             throw new SecurityException(msg);
         }
 
+        final int callingUid = Binder.getCallingUid();
+        final int callingPid = Binder.getCallingPid();
+
+        ProcessRecord proc;
+        synchronized (mPidsSelfLocked) {
+            proc = mPidsSelfLocked.get(callingPid);
+        }
+        if (callingUid >= FIRST_APPLICATION_UID
+                && (proc == null || !proc.info.isSystemApp())) {
+            final String msg = "Permission Denial: killAllBackgroundProcesses() from pid="
+                    + callingPid + ", uid=" + callingUid + " is not allowed";
+            Slog.w(TAG, msg);
+            // Silently return to avoid existing apps from crashing.
+            return;
+        }
+
         final long callingId = Binder.clearCallingIdentity();
         try {
             synchronized (this) {