Fix broken XML parsing idiom.

Code that expected a single top level element in an XML file
was doing something like :

while (type != START_TAG) { next(); }

This would loop forever when the XML being parsed was empty,
where each call to XmlPullParser.next() would return END_DOCUMENT.

bug: https://code.google.com/p/android/issues/detail?id=64173
Change-Id: I7543203e976a8999ae471a6c2d629249a87011bb

3 files changed, 19 insertions, 3 deletions

diff --git a/services/java/com/android/server/am/CompatModePackages.java b/services/java/com/android/server/am/CompatModePackages.java
index 59e6787..4d5577b 100644
--- a/services/java/com/android/server/am/CompatModePackages.java
+++ b/services/java/com/android/server/am/CompatModePackages.java
@@ -64,9 +64,14 @@ public final class CompatModePackages {
             XmlPullParser parser = Xml.newPullParser();
             parser.setInput(fis, null);
             int eventType = parser.getEventType();
-            while (eventType != XmlPullParser.START_TAG) {
+            while (eventType != XmlPullParser.START_TAG &&
+                    eventType != XmlPullParser.END_DOCUMENT) {
                 eventType = parser.next();
             }
+            if (eventType == XmlPullParser.END_DOCUMENT) {
+                return;
+            }
+
             String tagName = parser.getName();
             if ("compat-packages".equals(tagName)) {
                 eventType = parser.next();
diff --git a/services/java/com/android/server/am/UsageStatsService.java b/services/java/com/android/server/am/UsageStatsService.java
index e96d8b1..09cb344 100644
--- a/services/java/com/android/server/am/UsageStatsService.java
+++ b/services/java/com/android/server/am/UsageStatsService.java
@@ -396,9 +396,14 @@ public final class UsageStatsService extends IUsageStats.Stub {
             XmlPullParser parser = Xml.newPullParser();
             parser.setInput(fis, null);
             int eventType = parser.getEventType();
-            while (eventType != XmlPullParser.START_TAG) {
+            while (eventType != XmlPullParser.START_TAG &&
+                    eventType != XmlPullParser.END_DOCUMENT) {
                 eventType = parser.next();
             }
+            if (eventType == XmlPullParser.END_DOCUMENT) {
+                return;
+            }
+
             String tagName = parser.getName();
             if ("usage-history".equals(tagName)) {
                 String pkg = null;
diff --git a/services/java/com/android/server/content/SyncStorageEngine.java b/services/java/com/android/server/content/SyncStorageEngine.java
index 5ebf9ea..124bc60 100644
--- a/services/java/com/android/server/content/SyncStorageEngine.java
+++ b/services/java/com/android/server/content/SyncStorageEngine.java
@@ -1697,9 +1697,15 @@ public class SyncStorageEngine extends Handler {
             XmlPullParser parser = Xml.newPullParser();
             parser.setInput(fis, null);
             int eventType = parser.getEventType();
-            while (eventType != XmlPullParser.START_TAG) {
+            while (eventType != XmlPullParser.START_TAG &&
+                    eventType != XmlPullParser.END_DOCUMENT) {
                 eventType = parser.next();
             }
+            if (eventType == XmlPullParser.END_DOCUMENT) {
+                Log.i(TAG, "No initial accounts");
+                return;
+            }
+
             String tagName = parser.getName();
             if ("accounts".equals(tagName)) {
                 String listen = parser.getAttributeValue(null, XML_ATTR_LISTEN_FOR_TICKLES);