From a2debdb72470fa7d716eb2ad4c8607992c5d0be9 Mon Sep 17 00:00:00 2001
From: Alexey Zatelepin <ztlpn@yandex-team.ru>
Date: Fri, 15 Mar 2019 21:52:45 +0300
Subject: [PATCH] fix use-after-free [#CLICKHOUSE-3101]

---
 dbms/programs/server/TCPHandler.h        |  2 +-
 dbms/src/Storages/ColumnsDescription.cpp | 14 ++++++++++++++
 dbms/src/Storages/ColumnsDescription.h   | 14 +++++++++-----
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/dbms/programs/server/TCPHandler.h b/dbms/programs/server/TCPHandler.h
index 38ab27fd67b..a2febf20a20 100644
--- a/dbms/programs/server/TCPHandler.h
+++ b/dbms/programs/server/TCPHandler.h
@@ -25,7 +25,7 @@ namespace Poco { class Logger; }
 namespace DB
 {
 
-struct ColumnsDescription;
+class ColumnsDescription;
 
 /// State of query processing.
 struct QueryState
diff --git a/dbms/src/Storages/ColumnsDescription.cpp b/dbms/src/Storages/ColumnsDescription.cpp
index d3e50e94645..8bb818cd813 100644
--- a/dbms/src/Storages/ColumnsDescription.cpp
+++ b/dbms/src/Storages/ColumnsDescription.cpp
@@ -111,6 +111,20 @@ ColumnsDescription::ColumnsDescription(NamesAndTypesList ordinary)
         add(ColumnDescription(std::move(elem.name), std::move(elem.type)));
 }
 
+ColumnsDescription::ColumnsDescription(const ColumnsDescription & other)
+    : columns(other.columns)
+{
+    for (auto it = columns.begin(); it != columns.end(); ++it)
+        name_to_column.emplace(it->name, it);
+}
+
+ColumnsDescription & ColumnsDescription::operator=(const ColumnsDescription & other)
+{
+    if (&other != this)
+        *this = ColumnsDescription(other);
+    return *this;
+}
+
 
 /// We are trying to find first column from end with name `column_name` or with a name beginning with `column_name` and ".".
 /// For example "fruits.bananas"
diff --git a/dbms/src/Storages/ColumnsDescription.h b/dbms/src/Storages/ColumnsDescription.h
index d63d065fa74..8d400c8d1de 100644
--- a/dbms/src/Storages/ColumnsDescription.h
+++ b/dbms/src/Storages/ColumnsDescription.h
@@ -29,15 +29,15 @@ struct ColumnDescription
     void readText(ReadBuffer & buf);
 };
 
-struct ColumnsDescription
+class ColumnsDescription
 {
-private:
-    std::list<ColumnDescription> columns;
-    std::unordered_map<String, std::list<ColumnDescription>::iterator> name_to_column;
-
 public:
     ColumnsDescription() = default;
     explicit ColumnsDescription(NamesAndTypesList ordinary_);
+    ColumnsDescription(const ColumnsDescription & other);
+    ColumnsDescription & operator=(const ColumnsDescription & other);
+    ColumnsDescription(ColumnsDescription &&) noexcept = default;
+    ColumnsDescription & operator=(ColumnsDescription &&) noexcept = default;
 
     /// `after_column` can be a Nested column name;
     void add(ColumnDescription column, const String & after_column = String());
@@ -80,6 +80,10 @@ public:
     static ColumnsDescription parse(const String & str);
 
     static const ColumnsDescription * loadFromContext(const Context & context, const String & db, const String & table);
+
+private:
+    std::list<ColumnDescription> columns;
+    std::unordered_map<String, std::list<ColumnDescription>::iterator> name_to_column;
 };
 
 }