HADOOP-11409. FileContext.getFileContext can stack overflow if default fs misconfigured. Contributed by Gera Shegalov

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -617,6 +617,9 @@ Release 2.7.0 - UNRELEASED
     HADOOP-11385. Prevent cross site scripting attack on JMXJSONServlet.
     (wheat9)
 
+    HADOOP-11409. FileContext.getFileContext can stack overflow if default fs
+    misconfigured (Gera Shegalov via jlowe)
+
 Release 2.6.0 - 2014-11-18
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/AbstractFileSystem.java

@@ -148,11 +148,14 @@ static <T> T newInstance(Class<T> theClass,
    */
   public static AbstractFileSystem createFileSystem(URI uri, Configuration conf)
       throws UnsupportedFileSystemException {
-    Class<?> clazz = conf.getClass("fs.AbstractFileSystem." + 
+    final String fsImplConf = String.format("fs.AbstractFileSystem.%s.impl",
-                                uri.getScheme() + ".impl", null);
+        uri.getScheme());
+
+    Class<?> clazz = conf.getClass(fsImplConf, null);
     if (clazz == null) {
-      throw new UnsupportedFileSystemException(
+      throw new UnsupportedFileSystemException(String.format(
-          "No AbstractFileSystem for scheme: " + uri.getScheme());
+          "%s=null: No AbstractFileSystem configured for scheme: %s",
+          fsImplConf, uri.getScheme()));
     }
     return (AbstractFileSystem) newInstance(clazz, uri, conf);
   }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileContext.java

@@ -457,9 +457,15 @@ public static FileContext getFileContext(final URI defaultFsUri,
    */
   public static FileContext getFileContext(final Configuration aConf)
       throws UnsupportedFileSystemException {
-    return getFileContext(
+    final URI defaultFsUri = URI.create(aConf.get(FS_DEFAULT_NAME_KEY,
-      URI.create(aConf.get(FS_DEFAULT_NAME_KEY, FS_DEFAULT_NAME_DEFAULT)), 
+        FS_DEFAULT_NAME_DEFAULT));
-      aConf);
+    if (   defaultFsUri.getScheme() != null
+        && !defaultFsUri.getScheme().trim().isEmpty()) {
+      return getFileContext(defaultFsUri, aConf);
+    }
+    throw new UnsupportedFileSystemException(String.format(
+        "%s: URI configured via %s carries no scheme",
+        defaultFsUri, FS_DEFAULT_NAME_KEY));
   }
 
   /**

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestFileContext.java

@@ -0,0 +1,41 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.fs;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+import org.junit.Test;
+
+import static org.junit.Assert.fail;
+
+public class TestFileContext {
+  private static final Log LOG = LogFactory.getLog(TestFileContext.class);
+
+  @Test
+  public void testDefaultURIWithoutScheme() throws Exception {
+    final Configuration conf = new Configuration();
+    conf.set(FileSystem.FS_DEFAULT_NAME_KEY, "/");
+    try {
+      FileContext.getFileContext(conf);
+      fail(UnsupportedFileSystemException.class + " not thrown!");
+    } catch (UnsupportedFileSystemException ufse) {
+      LOG.info("Expected exception: ", ufse);
+    }
+  }
+}