Bug #64725 segfault using prepared select statement
Submitted: 21 Mar 2012 19:26 Modified: 3 Feb 2015 13:52
Reporter: Richard Kojedzinszky Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: C API (client library) Severity:S2 (Serious)
Version:5.5.40, 5.5.42, 5.6.23 OS:Linux (debian wheezy)
Assigned to: CPU Architecture:Any
Triage: Needs Triage: D2 (Serious)

[21 Mar 2012 19:26] Richard Kojedzinszky
Description:
I was using tntdb as a wrapper around mysql, but when a prepared select statement was executed multiple times, the application crashed. The crash came from libmysql. Attached a c app which does nearly the same calls as tntdb does.

How to repeat:

http://www38.zippyshare.com/v/84424887/file.html

If for some reason it does not segfault, the run it with valgrind -v, it'll show the invalid memory access.

Suggested fix:

Somehow it would be nice to inform the MYSQL_STMT structure that a MYSQL_BIND has disappeared.
[21 Mar 2012 21:05] Richard Kojedzinszky
The real example using tntdb

Attachment: test.cpp (text/x-c++src), 309 bytes.

[22 Mar 2012 12:17] Richard Kojedzinszky
C version of the attached file

Attachment: test.c (text/x-csrc), 2.49 KiB.

[25 Mar 2012 8:57] Valeriy Kravchuk
Bug #64754 is a duplicate of this one.
[10 May 2012 17:44] Sveta Smirnova
Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://dev.mysql.com/doc/ and the instructions on
how to report a bug at http://bugs.mysql.com/how-to-report.php

Problem is row #11: free(r->length);

You have not allocated memory with malloc for r->length, so looks like it is nothing to free. This is not MySQL bug.
[7 Jan 2015 16:05] Richard Kojedzinszky
Actually a more than two year bug report, still exists on 5.5.40. And after reading the docs, still dont see the wrong code in previously attached test files.
[13 Jan 2015 19:38] Sveta Smirnova
Thank you for the feedback.

You are correct: I misread your code. Verified as described on Linux using last development sources, compiled with debug option. With release version 5.6.21 on Mac bug is not repeatable.
[3 Feb 2015 13:52] Richard Kojedzinszky
Is there any updates/progress regarding this bug?