SERVER-21590 reject majority readConcern in PV0

1 files changed, 12 insertions, 0 deletions

diff --git a/src/mongo/db/dbcommands.cpp b/src/mongo/db/dbcommands.cpp
index a40f44dd210..9bd3abddc95 100644
--- a/src/mongo/db/dbcommands.cpp
+++ b/src/mongo/db/dbcommands.cpp
@@ -1389,6 +1389,18 @@ bool Command::run(OperationContext* txn,
                      repl::ReplicationCoordinator::Mode::modeReplSet ||
                  testingSnapshotBehaviorInIsolation) &&
                 readConcernArgs.getLevel() == repl::ReadConcernLevel::kMajorityReadConcern) {
+                // ReadConcern Majority is not supported in ProtocolVersion 0.
+                if (!replCoord->isV1ElectionProtocol()) {
+                    auto result = appendCommandStatus(
+                        inPlaceReplyBob,
+                        {ErrorCodes::ReadConcernMajorityNotEnabled,
+                         str::stream() << "Replica sets running protocol version 0 do not support "
+                                          "readConcern: majority"});
+                    inPlaceReplyBob.doneFast();
+                    replyBuilder->setMetadata(rpc::makeEmptyMetadata());
+                    return result;
+                }
+
                 Status status = txn->recoveryUnit()->setReadFromMajorityCommittedSnapshot();
 
                 // Wait until a snapshot is available.