Block loading WebView in privileged processes.

WebView is very powerful, but it also has a large attack area.  To
improve security, refuse to load WebView components when running as
the root or system UIDs.

Bug: 18376908
Change-Id: I515b819033586076b1a9668023bb43ee0295d003

core/java/android/webkit/WebViewFactory.java

@@ -17,8 +17,8 @@
 package android.webkit;
 
 import android.app.ActivityManagerInternal;
-import android.app.Application;
 import android.app.AppGlobals;
+import android.app.Application;
 import android.content.Context;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageInfo;
@@ -33,14 +33,14 @@ import android.os.Trace;
 import android.text.TextUtils;
 import android.util.AndroidRuntimeException;
 import android.util.Log;
+
 import com.android.server.LocalServices;
+
 import dalvik.system.VMRuntime;
 
 import java.io.File;
 import java.util.Arrays;
 
-import com.android.internal.os.Zygote;
-
 /**
  * Top level factory, used creating all the main WebView implementation classes.
  *
@@ -89,6 +89,12 @@ public final class WebViewFactory {
             // us honest and minimize usage of WebView internals when binding the proxy.
             if (sProviderInstance != null) return sProviderInstance;
 
+            final int uid = android.os.Process.myUid();
+            if (uid == android.os.Process.ROOT_UID || uid == android.os.Process.SYSTEM_UID) {
+                throw new UnsupportedOperationException(
+                        "For security reasons, WebView is not allowed in privileged processes");
+            }
+
             Trace.traceBegin(Trace.TRACE_TAG_WEBVIEW, "WebViewFactory.getProvider()");
             try {
                 Trace.traceBegin(Trace.TRACE_TAG_WEBVIEW, "WebViewFactory.loadNativeLibrary()");