From 89a96cf14d846b2e2b8e47062125992028b69588 Mon Sep 17 00:00:00 2001
From: Azat Khuzhin <a3at.mail@gmail.com>
Date: Sun, 4 Apr 2021 08:23:12 +0300
Subject: [PATCH] StorageLog: avoid UB for rwlock unlock due to unlock from
 another thread

---
 src/Storages/StorageLog.cpp                             | 5 +++++
 tests/queries/0_stateless/01796_Log_rwlock_ub.reference | 0
 tests/queries/0_stateless/01796_Log_rwlock_ub.sql       | 5 +++++
 3 files changed, 10 insertions(+)
 create mode 100644 tests/queries/0_stateless/01796_Log_rwlock_ub.reference
 create mode 100644 tests/queries/0_stateless/01796_Log_rwlock_ub.sql

diff --git a/src/Storages/StorageLog.cpp b/src/Storages/StorageLog.cpp
index ddb0cadc148..9fdd466e792 100644
--- a/src/Storages/StorageLog.cpp
+++ b/src/Storages/StorageLog.cpp
@@ -357,6 +357,11 @@ void LogBlockOutputStream::writeSuffix()
 
     streams.clear();
     done = true;
+
+    /// unlock should be done from the same thread as lock, and dtor may be
+    /// called from different thread, so it should be done here (at least in
+    /// case of no exceptions occurred)
+    lock.unlock();
 }
 
 
diff --git a/tests/queries/0_stateless/01796_Log_rwlock_ub.reference b/tests/queries/0_stateless/01796_Log_rwlock_ub.reference
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/queries/0_stateless/01796_Log_rwlock_ub.sql b/tests/queries/0_stateless/01796_Log_rwlock_ub.sql
new file mode 100644
index 00000000000..4f95dbc14e5
--- /dev/null
+++ b/tests/queries/0_stateless/01796_Log_rwlock_ub.sql
@@ -0,0 +1,5 @@
+DROP TABLE IF EXISTS underlying_01796;
+CREATE TABLE underlying_01796 (key UInt64) Engine=Log();
+INSERT INTO FUNCTION remote('127.1', currentDatabase(), underlying_01796) SELECT toUInt64(number) FROM system.numbers LIMIT 1;
+SELECT * FROM underlying_01796 FORMAT Null;
+DROP TABLE underlying_01796;