https://www.undeadly.org/cgi?action=article;sid=20230417074903

Front page
[                    ] [Search site]
OpenBSD Journal

Home Archives About Submit Story Create Account Login

malloc leak detection available in -current

Contributed by Peter N. M. Hansteen on 2023-04-17 from the freeing
the chunks dept.

OpenBSD -current just grew a new tool for developers working on
OpenBSD to detect unsafe behaviors in their code. OpenBSD lets you
more easily track memory allocations and whether allocations are
properly freed after use.

In a message to tech@, Otto Moerbeek (otto@) announced the new
functionality:

    Subject:    malloc leak detection available in -current
    From:       Otto Moerbeek <otto () drijf ! net>
    Date:       2023-04-17 6:43:19

    Hi,

    OpenBSD current now has built-in malloc leak detection.

    Make sure you run current and have debug symbols (OpenBSD base
    libraries have debug symbols, compile your own program with -g).

    To record the leak report:
    $ MALLOC_OPTIONS=D ktrace -tu a.out

    To view the leak report:
    $ kdump -u malloc

    Example output:

    ******** Start dump a.out *******
    M=8 I=1 F=0 U=0 J=1 R=0 X=0 C=0 cache=64 G=0
    Leak report:
                     f     sum      #    avg
                   0x0 1088864   9722    112 addr2line -e '?' 0x0
           0xf4b73093c   31136    278    112 addr2line -e a.out 0x1093c

    ******** End dump a.out *******

    $ addr2line -e a.out 0x1093c
    /home/otto/x.c:6

    Some additional info:

    The null "f" values (call sites) are due to the sampling nature of
    small allocations. Recording all call sites of all potential leaks
    introduces too much overhead.

    Note that aggresssive optimizations might confuse the line numbers
    reported.

    For -static programs, compile with -nopie to make addr2line work.

    In some cases will want to use the packaged version of addr2line
    (gaddr2line, in the binutils package) as the base addr2line does not
    grok all debug info formats.

            -Otto


This represents one important step in the ongoing work of making
OpenBSD the better environment for developing secure, well behaved
code.

Reply

---------------------------------------------------------------------
Comments

 1. By John McCue (jmcunx) jmcq66@comcast.net on 2023-04-17 18:56

    It is like the OpenBSD developers read my mind :)

    Thank you!

    Reply

Latest Articles

  * Mon, Apr 17
      + 07:49 malloc leak detection available in -current (1)
  * Mon, Apr 10
      + 14:00 OpenBSD 7.3 released (2)
  * Sun, Apr 09
      + 11:07 LibreSSL 3.7.2 Released (0)
  * Sat, Mar 25
      + 16:34 Theo de Raadt at CanSecWest: Synthetic Memory
        Protections (0)
  * Thu, Mar 23
      + 15:23 OpenBGPD 7.9 released (0)
  * Sun, Mar 19
      + 23:05 (Even more) Aggressive randomisation of stack location
        (0)
      + 22:56 rpki-client 8.3 released (0)
  * Sat, Mar 18
      + 11:26 -current has moved to 7.3, ports commits restricted
        pending release (0)
      + 09:13 OpenBGPD 7.8 released (0)

Credits

Copyright (c) 2004-2008 Daniel Hartmeier. All rights reserved. Articles
and comments are copyright their respective authors, submission
implies license to publish on this web site. Contents of the archive
prior to April 2nd 2004 as well as images and HTML templates were
copied from the fabulous original deadly.org with Jose's and Jim's
kind permission. This journal runs as CGI with httpd(8) on OpenBSD,
the source code is BSD licensed. undeadly \Un*dead"ly\, a. Not
subject to death; immortal. [Obs.]