diff --git a/hadoop-common-project/hadoop-nfs/src/main/java/org/apache/hadoop/nfs/nfs3/response/ACCESS3Response.java b/hadoop-common-project/hadoop-nfs/src/main/java/org/apache/hadoop/nfs/nfs3/response/ACCESS3Response.java
index 8ba07aa5b3..5720fc6479 100644
--- a/hadoop-common-project/hadoop-nfs/src/main/java/org/apache/hadoop/nfs/nfs3/response/ACCESS3Response.java
+++ b/hadoop-common-project/hadoop-nfs/src/main/java/org/apache/hadoop/nfs/nfs3/response/ACCESS3Response.java
@@ -46,10 +46,12 @@ public ACCESS3Response(int status, Nfs3FileAttributes postOpAttr, int access) {
   @Override
   public XDR writeHeaderAndResponse(XDR out, int xid, Verifier verifier) {
     super.writeHeaderAndResponse(out, xid, verifier);
-    out.writeBoolean(true);
-    postOpAttr.serialize(out);
     if (this.getStatus() == Nfs3Status.NFS3_OK) {
+      out.writeBoolean(true);
+      postOpAttr.serialize(out);
       out.writeInt(access);
+    } else {
+      out.writeBoolean(false);
     }
     return out;
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs-nfs/src/main/java/org/apache/hadoop/hdfs/nfs/nfs3/RpcProgramNfs3.java b/hadoop-hdfs-project/hadoop-hdfs-nfs/src/main/java/org/apache/hadoop/hdfs/nfs/nfs3/RpcProgramNfs3.java
index f78598f13a..62aa8cbedc 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-nfs/src/main/java/org/apache/hadoop/hdfs/nfs/nfs3/RpcProgramNfs3.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-nfs/src/main/java/org/apache/hadoop/hdfs/nfs/nfs3/RpcProgramNfs3.java
@@ -124,6 +124,7 @@
 import org.apache.hadoop.security.AccessControlException;
 import org.apache.hadoop.security.SecurityUtil;
 import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.security.authorize.AuthorizationException;
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
@@ -270,6 +271,17 @@ public GETATTR3Response getattr(XDR xdr, SecurityHandler securityHandler,
     Nfs3FileAttributes attrs = null;
     try {
       attrs = writeManager.getFileAttr(dfsClient, handle, iug);
+    } catch (RemoteException r) {
+      LOG.warn("Exception ", r);
+      IOException io = r.unwrapRemoteException();
+      /**
+       * AuthorizationException can be thrown if the user can't be proxy'ed.
+       */
+      if (io instanceof AuthorizationException) {
+        return new GETATTR3Response(Nfs3Status.NFS3ERR_ACCES);
+      } else {
+        return new GETATTR3Response(Nfs3Status.NFS3ERR_IO);
+      }
     } catch (IOException e) {
       LOG.info("Can't get file attribute, fileId=" + handle.getFileId(), e);
       response.setStatus(Nfs3Status.NFS3ERR_IO);
@@ -499,6 +511,17 @@ public ACCESS3Response access(XDR xdr, SecurityHandler securityHandler,
           securityHandler.getUid(), securityHandler.getGid(), attrs);
       
       return new ACCESS3Response(Nfs3Status.NFS3_OK, attrs, access);
+    } catch (RemoteException r) {
+      LOG.warn("Exception ", r);
+      IOException io = r.unwrapRemoteException();
+      /**
+       * AuthorizationException can be thrown if the user can't be proxy'ed.
+       */
+      if (io instanceof AuthorizationException) {
+        return new ACCESS3Response(Nfs3Status.NFS3ERR_ACCES);
+      } else {
+        return new ACCESS3Response(Nfs3Status.NFS3ERR_IO);
+      }
     } catch (IOException e) {
       LOG.warn("Exception ", e);
       return new ACCESS3Response(Nfs3Status.NFS3ERR_IO);
@@ -1680,6 +1703,17 @@ public FSSTAT3Response fsstat(XDR xdr, SecurityHandler securityHandler,
       
       return new FSSTAT3Response(Nfs3Status.NFS3_OK, attrs, totalBytes,
           freeBytes, freeBytes, maxFsObjects, maxFsObjects, maxFsObjects, 0);
+    } catch (RemoteException r) {
+      LOG.warn("Exception ", r);
+      IOException io = r.unwrapRemoteException();
+      /**
+       * AuthorizationException can be thrown if the user can't be proxy'ed.
+       */
+      if (io instanceof AuthorizationException) {
+        return new FSSTAT3Response(Nfs3Status.NFS3ERR_ACCES);
+      } else {
+        return new FSSTAT3Response(Nfs3Status.NFS3ERR_IO);
+      }
     } catch (IOException e) {
       LOG.warn("Exception ", e);
       return new FSSTAT3Response(Nfs3Status.NFS3ERR_IO);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index d1b9f391d9..5814821b0e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -681,6 +681,9 @@ Release 2.4.1 - UNRELEASED
     HDFS-6397. NN shows inconsistent value in deadnode count.
     (Mohammad Kamrul Islam via kihwal)
 
+    HDFS-6411. nfs-hdfs-gateway mount raises I/O error and hangs when a 
+    unauthorized user attempts to access it (brandonli)
+
 Release 2.4.0 - 2014-04-07 
 
   INCOMPATIBLE CHANGES