From 126cecc6366342ffe9d4561ba6ff7532f596c019 Mon Sep 17 00:00:00 2001
From: Misha Tyulenev <misha@mongodb.com>
Date: Mon, 14 Dec 2015 19:19:03 -0500
Subject: [PATCH] SERVER-21706 error when mapReduce outputs to config or admin
 db

(cherry picked from commit 3e1a3872c996fcc72c8cf20ea38e9fe86a11caa4)
---
 jstests/sharding/map_reduce_validation.js | 16 ++++++++++++++++
 src/mongo/db/commands/mr.cpp              |  8 ++++++++
 2 files changed, 24 insertions(+)

diff --git a/jstests/sharding/map_reduce_validation.js b/jstests/sharding/map_reduce_validation.js
index f85c47f3831..9fe08edd91a 100644
--- a/jstests/sharding/map_reduce_validation.js
+++ b/jstests/sharding/map_reduce_validation.js
@@ -10,4 +10,20 @@ assert.commandFailed(testDB.runCommand({ mapReduce: 'user',
                                          reduce: reduceFunc,
                                          out: { inline: 1, sharded: true }}));
 
+testDB.bar.insert({i: 1});
+assert.commandFailed(testDB.runCommand({ mapReduce: 'bar',
+                                         map: function() {emit(this.i, this.i*3);},
+                                         reduce:  function(key, values) {return Array.sum(values)},
+                                         out: { replace: "foo", db: "admin" }}));
+
+assert.commandFailed(testDB.runCommand({ mapReduce: 'bar',
+                                         map: function() {emit(this.i, this.i*3);},
+                                         reduce:  function(key, values) {return Array.sum(values)},
+                                         out: { replace: "foo", db: "config" }}));
+
+assert.commandWorked(testDB.runCommand({ mapReduce: 'bar',
+                                         map: function() {emit(this.i, this.i*3);},
+                                         reduce:  function(key, values) {return Array.sum(values)},
+                                         out: { replace: "foo", db: "test" }}));
+
 st.stop();
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index 2d050c924f1..d0066e7e066 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -1566,6 +1566,14 @@ public:
              int,
              string& errmsg,
              BSONObjBuilder& result) {
+        if (!grid.shardRegistry()) {
+            return appendCommandStatus(
+                result,
+                Status(ErrorCodes::CommandNotSupported,
+                       str::stream() << "Can not execute mapReduce with output database "
+                                     << dbname));
+        }
+
         boost::optional<DisableDocumentValidation> maybeDisableValidation;
         if (shouldBypassDocumentValidationForCommand(cmdObj))
             maybeDisableValidation.emplace(txn);