Don't mix "current dataset" tokens for different backup transports

Previously, one could poison the current-dataset tracking by
inopportunely-timed use of the local (aka development) transport.
Now you can't:  we reset the 'current dataset token?' tracking
whenever the user changes the active transport.

Also don't double-allocate return values sometimes.

Bug 37694618
Test: manual

Change-Id: I2cf5d42774522af830aecb99e65f43c4d0b5ce76

2 files changed, 27 insertions, 8 deletions

diff --git a/services/backup/java/com/android/server/backup/BackupManagerService.java b/services/backup/java/com/android/server/backup/BackupManagerService.java
index 1b970e5656bd..b0340ea63051 100644
--- a/services/backup/java/com/android/server/backup/BackupManagerService.java
+++ b/services/backup/java/com/android/server/backup/BackupManagerService.java
@@ -2387,7 +2387,7 @@ public class BackupManagerService {
 
         long token = mAncestralToken;
         synchronized (mQueueLock) {
-            if (mEverStoredApps.contains(packageName)) {
+            if (mCurrentToken != 0 && mEverStoredApps.contains(packageName)) {
                 if (MORE_DEBUG) {
                     Slog.i(TAG, "App in ever-stored, so using current token");
                 }
@@ -10456,8 +10456,7 @@ if (MORE_DEBUG) Slog.v(TAG, "   + got " + nRead + "; now wanting " + (size - soF
         final long oldId = Binder.clearCallingIdentity();
         try {
             String prevTransport = mTransportManager.selectTransport(transport);
-            Settings.Secure.putString(mContext.getContentResolver(),
-                    Settings.Secure.BACKUP_TRANSPORT, transport);
+            updateStateForTransport(transport);
             Slog.v(TAG, "selectBackupTransport() set " + mTransportManager.getCurrentTransportName()
                     + " returning " + prevTransport);
             return prevTransport;
@@ -10480,9 +10479,7 @@ if (MORE_DEBUG) Slog.v(TAG, "   + got " + nRead + "; now wanting " + (size - soF
             @Override
             public void onSuccess(String transportName) {
                 mTransportManager.selectTransport(transportName);
-                Settings.Secure.putString(mContext.getContentResolver(),
-                        Settings.Secure.BACKUP_TRANSPORT,
-                        mTransportManager.getCurrentTransportName());
+                updateStateForTransport(mTransportManager.getCurrentTransportName());
                 Slog.v(TAG, "Transport successfully selected: " + transport.flattenToShortString());
                 try {
                     listener.onSuccess(transportName);
@@ -10505,6 +10502,28 @@ if (MORE_DEBUG) Slog.v(TAG, "   + got " + nRead + "; now wanting " + (size - soF
         Binder.restoreCallingIdentity(oldId);
     }
 
+    private void updateStateForTransport(String newTransportName) {
+        // Publish the name change
+        Settings.Secure.putString(mContext.getContentResolver(),
+                Settings.Secure.BACKUP_TRANSPORT, newTransportName);
+
+        // And update our current-dataset bookkeeping
+        IBackupTransport transport = mTransportManager.getTransportBinder(newTransportName);
+        if (transport != null) {
+            try {
+                mCurrentToken = transport.getCurrentRestoreSet();
+            } catch (Exception e) {
+                // Oops.  We can't know the current dataset token, so reset and figure it out
+                // when we do the next k/v backup operation on this transport.
+                mCurrentToken = 0;
+            }
+        } else {
+            // The named transport isn't bound at this particular moment, so we can't
+            // know yet what its current dataset token is.  Reset as above.
+            mCurrentToken = 0;
+        }
+    }
+
     // Supply the configuration Intent for the given transport.  If the name is not one
     // of the available transports, or if the transport does not supply any configuration
     // UI, the method returns null.
diff --git a/services/backup/java/com/android/server/backup/TransportManager.java b/services/backup/java/com/android/server/backup/TransportManager.java
index 67f105e503d3..da1f32c9d203 100644
--- a/services/backup/java/com/android/server/backup/TransportManager.java
+++ b/services/backup/java/com/android/server/backup/TransportManager.java
@@ -182,13 +182,13 @@ class TransportManager {
 
     String[] getBoundTransportNames() {
         synchronized (mTransportLock) {
-            return mBoundTransports.keySet().toArray(new String[0]);
+            return mBoundTransports.keySet().toArray(new String[mBoundTransports.size()]);
         }
     }
 
     ComponentName[] getAllTransportCompenents() {
         synchronized (mTransportLock) {
-            return mValidTransports.keySet().toArray(new ComponentName[0]);
+            return mValidTransports.keySet().toArray(new ComponentName[mValidTransports.size()]);
         }
     }