From 8718323a765a50721425259ebaf5a7bfcbe14273 Mon Sep 17 00:00:00 2001
From: Hall Liu <hallliu@google.com>
Date: Thu, 3 Oct 2019 11:48:31 -0700
Subject: [PATCH] Fix race in TelephonyScanManager

TelephonyScanManager may sometimes encounter a race condition where
Telephony sends it the first scan result before it has saved the
returned scan ID. This causes a crash in the app that's requesting the
scan.

To fix this, synchronize on mScanInfo while requesting the network scan
so that the handler in TelephonyScanManager will wait for the scan ID to
be saved before processing the first message from Telephony.

Bug: 142068098
Test: manual
Change-Id: I0b2b4c6dc749e21641843818293941704ed870a6
---
 .../telephony/TelephonyScanManager.java       | 22 +++++++++----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/telephony/java/android/telephony/TelephonyScanManager.java b/telephony/java/android/telephony/TelephonyScanManager.java
index 28747dab38dbb..9ff8515986486 100644
--- a/telephony/java/android/telephony/TelephonyScanManager.java
+++ b/telephony/java/android/telephony/TelephonyScanManager.java
@@ -104,7 +104,7 @@ public final class TelephonyScanManager {
 
     private final Looper mLooper;
     private final Messenger mMessenger;
-    private SparseArray<NetworkScanInfo> mScanInfo = new SparseArray<NetworkScanInfo>();
+    private final SparseArray<NetworkScanInfo> mScanInfo = new SparseArray<NetworkScanInfo>();
 
     public TelephonyScanManager() {
         HandlerThread thread = new HandlerThread(TAG);
@@ -204,14 +204,16 @@ public final class TelephonyScanManager {
         try {
             ITelephony telephony = getITelephony();
             if (telephony != null) {
-                int scanId = telephony.requestNetworkScan(
-                        subId, request, mMessenger, new Binder(), callingPackage);
-                if (scanId == INVALID_SCAN_ID) {
-                    Rlog.e(TAG, "Failed to initiate network scan");
-                    return null;
+                synchronized (mScanInfo) {
+                    int scanId = telephony.requestNetworkScan(
+                            subId, request, mMessenger, new Binder(), callingPackage);
+                    if (scanId == INVALID_SCAN_ID) {
+                        Rlog.e(TAG, "Failed to initiate network scan");
+                        return null;
+                    }
+                    saveScanInfo(scanId, request, executor, callback);
+                    return new NetworkScan(scanId, subId);
                 }
-                saveScanInfo(scanId, request, executor, callback);
-                return new NetworkScan(scanId, subId);
             }
         } catch (RemoteException ex) {
             Rlog.e(TAG, "requestNetworkScan RemoteException", ex);
@@ -223,9 +225,7 @@ public final class TelephonyScanManager {
 
     private void saveScanInfo(
             int id, NetworkScanRequest request, Executor executor, NetworkScanCallback callback) {
-        synchronized (mScanInfo) {
-            mScanInfo.put(id, new NetworkScanInfo(request, executor, callback));
-        }
+        mScanInfo.put(id, new NetworkScanInfo(request, executor, callback));
     }
 
     private ITelephony getITelephony() {