| Bug #93925 | Possible memory leak in libmysqlclient20 | ||
|---|---|---|---|
| Submitted: | 15 Jan 2019 0:18 | Modified: | 22 Jan 2019 11:34 |
| Reporter: | Arjuna Del Toso | Email Updates: | |
| Status: | Not a Bug | Impact on me: | |
| Category: | MySQL Server: C API (client library) | Severity: | S3 (Non-critical) |
| Version: | 5.7.24 | OS: | Linux |
| Assigned to: | MySQL Verification Team | CPU Architecture: | Any |
[15 Jan 2019 0:19]
Arjuna Del Toso
The code exposing the issue
Attachment: mysql-bug.c (text/x-csrc), 2.75 KiB.
[22 Jan 2019 11:34]
MySQL Verification Team
Hi, Thanks for report, but this is not a bug yes, when I run your code: [arhimed@localhost ~]$ gcc -g -O0 bug93925.c -o mysql-bug -I/home/arhimed/mysql/5.7.24/include/mysql/ -I/home/arhimed/mysql/5.7.24/include/ -L/home/arhimed/mysql/5.7.24/lib/ -lmysqlclient [arhimed@localhost ~]$ LD_LIBRARY_PATH=/home/arhimed/mysql/5.7.24/lib ./mysql-bug 2 row: a row: b [arhimed@localhost ~]$ LD_LIBRARY_PATH=/home/arhimed/mysql/5.7.24/lib valgrind --leak-check=yes ./mysql-bug 2 ==67433== Memcheck, a memory error detector ==67433== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al. ==67433== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info ==67433== Command: ./mysql-bug 2 ==67433== row: a row: b ==67433== ==67433== HEAP SUMMARY: ==67433== in use at exit: 79,976 bytes in 5 blocks ==67433== total heap usage: 86 allocs, 81 frees, 173,176 bytes allocated ==67433== ==67433== 7,272 (912 direct, 6,360 indirect) bytes in 1 blocks are definitely lost in loss record 4 of 5 ==67433== at 0x4C2A988: calloc (vg_replace_malloc.c:711) ==67433== by 0x4E94D06: my_raw_malloc (my_malloc.c:189) ==67433== by 0x4E94D06: my_malloc (my_malloc.c:54) ==67433== by 0x4E5F22A: mysql_stmt_init (libmysql.c:1552) ==67433== by 0x400DF7: main (bug93925.c:46) ==67433== ==67433== LEAK SUMMARY: ==67433== definitely lost: 912 bytes in 1 blocks ==67433== indirectly lost: 6,360 bytes in 3 blocks ==67433== possibly lost: 0 bytes in 0 blocks ==67433== still reachable: 0 bytes in 0 blocks ==67433== suppressed: 72,704 bytes in 1 blocks ==67433== ==67433== For counts of detected and suppressed errors, rerun with: -v ==67433== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0) [arhimed@localhost ~]$
[22 Jan 2019 11:38]
MySQL Verification Team
but when I "fix" your code: [arhimed@localhost ~]$ diff bug93925-original.c bug93925-fixed.c 112c112,113 < if (mysql_stmt_free_result(stmt) != 0) fwprintf(stderr, L"unable to free stmt"); --- > if (mysql_stmt_free_result(stmt) != 0) fwprintf(stderr, L"unable to free result"); > if (mysql_stmt_close(stmt) != 0) fwprintf(stderr, L"unable to free stmt"); as you forgot to free the statement, your error for freeing result mentions statement but actually you have to free result (you are doing it properly but with wrong error msg) and then you need to (and you forgot) free the actual statement with https://dev.mysql.com/doc/refman/5.7/en/mysql-stmt-close.html you get: [arhimed@localhost ~]$ LD_LIBRARY_PATH=/home/arhimed/mysql/5.7.24/lib valgrind --leak-check=yes ./mysql-bug 2 ==67460== Memcheck, a memory error detector ==67460== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al. ==67460== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info ==67460== Command: ./mysql-bug 2 ==67460== row: a row: b ==67460== ==67460== HEAP SUMMARY: ==67460== in use at exit: 72,704 bytes in 1 blocks ==67460== total heap usage: 86 allocs, 85 frees, 173,176 bytes allocated ==67460== ==67460== LEAK SUMMARY: ==67460== definitely lost: 0 bytes in 0 blocks ==67460== indirectly lost: 0 bytes in 0 blocks ==67460== possibly lost: 0 bytes in 0 blocks ==67460== still reachable: 0 bytes in 0 blocks ==67460== suppressed: 72,704 bytes in 1 blocks ==67460== ==67460== For counts of detected and suppressed errors, rerun with: -v ==67460== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0) all best Bogdan
Description: On code mostly copy/pasted from the official documentation valgrind reports the following leak ==5525== 7,272 (912 direct, 6,360 indirect) bytes in 1 blocks are definitely lost in loss record 4 of 4 ==5525== at 0x4C31B25: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==5525== by 0x4EA1F8B: ??? (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.11) ==5525== by 0x4E6397A: mysql_stmt_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.11) ==5525== by 0x108F06: main (mysql-bug.c:46) ==5525== ==5525== LEAK SUMMARY: ==5525== definitely lost: 912 bytes in 1 blocks ==5525== indirectly lost: 6,360 bytes in 3 blocks How to repeat: Follow these instructions on a machine with docker: $ docker run -d --name ubu --entrypoint "tail" ubuntu -f /dev/null $ docker cp mysql-bug.c ubu:. $ docker exec -it ubu bash root@d4537d06b4b8:/# apt-get update && apt-get install -y build-essential libcurl4-openssl-dev libmysqlclient-dev valgrind clang-tools-6.0 mysql-server root@d4537d06b4b8:/# service mysql start root@d4537d06b4b8:/# echo 'CREATE DATABASE db CHARACTER SET utf8 COLLATE utf8_general_ci; USE db; CREATE TABLE tbl (url VARCHAR(260)); INSERT INTO tbl VALUES ("a"), ("b"), ("c");' | mysql -uroot -p root@d4537d06b4b8:/# cc -g -O0 mysql-bug.c -o mysql-bug -I/usr/include/mysql/ -lmysqlclient root@d4537d06b4b8:/# valgrind --leak-check=yes ./mysql-bug 2 ==5525== Memcheck, a memory error detector ==5525== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al. ==5525== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info ==5525== Command: ./mysql-bug 2 ==5525== row: a row: b ==5525== ==5525== HEAP SUMMARY: ==5525== in use at exit: 7,272 bytes in 4 blocks ==5525== total heap usage: 80 allocs, 76 frees, 185,983 bytes allocated ==5525== ==5525== 7,272 (912 direct, 6,360 indirect) bytes in 1 blocks are definitely lost in loss record 4 of 4 ==5525== at 0x4C31B25: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==5525== by 0x4EA1F8B: ??? (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.11) ==5525== by 0x4E6397A: mysql_stmt_init (in /usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.11) ==5525== by 0x108F06: main (mysql-bug.c:46) ==5525== ==5525== LEAK SUMMARY: ==5525== definitely lost: 912 bytes in 1 blocks ==5525== indirectly lost: 6,360 bytes in 3 blocks ==5525== possibly lost: 0 bytes in 0 blocks ==5525== still reachable: 0 bytes in 0 blocks ==5525== suppressed: 0 bytes in 0 blocks ==5525== ==5525== For counts of detected and suppressed errors, rerun with: -v ==5525== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0) root@d4537d06b4b8:/# dpkg -l libmysqlclient20* valgrind Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad) ||/ Name Version Architecture Description +++-=====================================================-===============================-===============================-================================================================================================================ ii libmysqlclient20:amd64 5.7.24-0ubuntu0.18.04.1 amd64 MySQL database client library ii valgrind 1:3.13.0-2ubuntu2.1 amd64 instrumentation framework for building dynamic analysis tools root@d4537d06b4b8:/# cc --version cc (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0 Copyright (C) 2017 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. root@d4537d06b4b8:/# uname -a Linux d4537d06b4b8 4.15.0-42-generic #45~16.04.1-Ubuntu SMP Mon Nov 19 13:02:27 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux