MXS-2727 Add test that reveals problem

server/modules/filter/cache/test/CMakeLists.txt

@@ -46,6 +46,11 @@ target_link_libraries(test_cacheoptions maxscale-common)
 add_executable(cache_stress cache_stress.cc)
 target_link_libraries(cache_stress ${MARIADB_CONNECTOR_LIBRARIES} ssl crypt crypto dl pthread)
 
+add_executable(cache_bugs cache_bugs.cc)
+target_link_libraries(cache_bugs cache maxscale-common mysqlcommon)
+
+add_test(test_cache_bugs cache_bugs)
+
 add_test(test_cache_rules testrules)
 
 add_test(test_cache_inmemory_keygeneration testkeygeneration storage_inmemory ${CMAKE_CURRENT_SOURCE_DIR}/input.test)

server/modules/filter/cache/test/cache_bugs.cc

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2023-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/ccdefs.hh>
+#include <iostream>
+#include <string>
+#include <vector>
+#include <maxbase/log.hh>
+#include <maxscale/modinfo.h>
+#include "../cachemt.hh"
+
+using namespace std;
+
+namespace
+{
+
+GWBUF* create_gwbuf(const string& s)
+{
+    size_t len = s.length();
+    size_t payload_len = len + 1;
+    size_t gwbuf_len = MYSQL_HEADER_LEN + payload_len;
+
+    GWBUF* pBuf = gwbuf_alloc(gwbuf_len);
+
+    *((unsigned char*)((char*)GWBUF_DATA(pBuf))) = payload_len;
+    *((unsigned char*)((char*)GWBUF_DATA(pBuf) + 1)) = (payload_len >> 8);
+    *((unsigned char*)((char*)GWBUF_DATA(pBuf) + 2)) = (payload_len >> 16);
+    *((unsigned char*)((char*)GWBUF_DATA(pBuf) + 3)) = 0x00;
+    *((unsigned char*)((char*)GWBUF_DATA(pBuf) + 4)) = 0x03;
+    memcpy((char*)GWBUF_DATA(pBuf) + 5, s.c_str(), len);
+
+    return pBuf;
+}
+
+int mxs_2727()
+{
+    int rv = 0;
+
+    const size_t MAX_SIZE = 10;
+
+    CacheConfig config("MXS-2727");
+    config.storage = std::string("storage_inmemory");
+    config.soft_ttl = std::chrono::seconds(1);
+    config.hard_ttl = std::chrono::seconds(10);
+    config.max_size = MAX_SIZE;
+    config.thread_model = CACHE_THREAD_MODEL_MT;
+    config.enabled = true;
+
+    auto* pCache = CacheMT::Create("MXS-2727", &config);
+
+    CACHE_KEY key;
+    GWBUF* pSelect = create_gwbuf("SELECT * FROM t");
+
+    cache_result_t result = pCache->get_key("test", pSelect, &key);
+
+    if (!CACHE_RESULT_IS_OK(result))
+    {
+        return 1;
+    }
+
+    vector<uint8_t> value(MAX_SIZE - 1); // Less than max size.
+    std::generate(value.begin(), value.end(), random);
+
+    GWBUF* pValue = gwbuf_alloc_and_load(value.size(), &value.front());
+
+    result = pCache->put_value(key, pValue);
+    gwbuf_free(pValue);
+
+    if (!CACHE_RESULT_IS_OK(result))
+    {
+        return 1;
+    }
+
+    value.push_back(4);
+    value.push_back(2);
+    // Now, larger than max size.
+
+    pValue = gwbuf_alloc_and_load(value.size(), &value.front());
+
+    // This will crash without the MXS-2727 fix.
+    result = pCache->put_value(key, pValue);
+    gwbuf_free(pValue);
+
+    if (!CACHE_RESULT_IS_OK(result))
+    {
+        return 1;
+    }
+
+    return 0;
+}
+
+}
+
+int main()
+{
+    mxb::Log log;
+
+    int rv = 0;
+
+    rv += mxs_2727();
+
+    return rv == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
+}