Fwd: Segmentation Fault: madwifi and hostapd
chadlich at yahoo.com
Tue Jan 31 20:30:08 EST 2006
Setting logger_stdout=0 did the trick. Hostapd no
longer seg faults. At this point, I must confess that
I'm lost. I'm at a loss, primary, because I don't
understand the hostapd log settings. Setting the
bitfields of the logger_syslog, etc, based on the the
config setting instructions, just isn't that intuitive
One thing I noticed is that when I ran hostapd with my
WPA-PSK setup (with the same logger_* settings, I
didn't have any problems with seg faults. But then,
walking through the code, my WPA-PSK setup doesn't
What do you think is the source of the problem: glib?,
hostapd?, my config file?
--- Jouni Malinen <jkmaline at cc.hut.fi> wrote:
> On Mon, Jan 30, 2006 at 07:24:56PM -0800, Chad
> Meister wrote:
> > I've done some further investigations using gdb.
> > Looking at the valgrind output, I decided to
> > investigate the suspicious conditionals. One
> > is line 135 in hostap.c:
> > if ((conf_syslog & module) && level >=
> > conf_syslog_level)
> > valgrind output suggests that there is an
> > value in this conditional, before it drops into
> > vsyslog() and seg faults.
> Hmm.. I did not notice messages about that line in
> the valgrind output.
> The main warnings were being triggered inside glibc
> in vfprintf (called
> from vsyslog).
> > After further
> > investigation, I think the uninitialized variable
> > the conf_syslog. The value of conf_syslog is
> based on
> > the hostapd_config struct's unsigned int
> > value - a variable used for bitwise operations.
> > default value of logger_syslog is an (unsigned
> > -1.
> I don't see how this could be uninitialized.
> > In my setup, this is where I think things go
> > When hostapd sets logger_syslog value as a
> > int) -1, the value "4294967295" is assigned.
> This is the expected behavior and that (unsigned
> int) -1 is just a more
> or less standard mechanism for setting a variable to
> a value with all
> bits set to 1.
> > I think this happens with all -1 (unsigned int)
> > assignments on my machine. When I manually set
> > conf_syslog to 0 back in gdb, hostapd does not
> > segfault and descends into the radius code to
> > the connection.
> The segfault is clearly related to vsyslog call.
> Setting conf_syslog to
> 0 is just skipping that call which avoids the
> > So what is going on here?
> I'm not sure. I cannot reproduce the same behavior
> in my tests with
> valgrind on x86. Just in case, I ran a test with
> hostapd on PowerPC;
> though, I'm using different C library, so vsyslog is
> One possible explanation could be that something is
> going wrong with
> variable argument processing
> (va_start/va_list/va_end). hostapd_logger()
> is passing variable arguments into two functions in
> your configuration
> case. Could you please try what happens if you leave
> but change logger_stdout=0 in the configuration.
> This will make only
> vsyslog() to use the variable arguments.
> Jouni Malinen
> PGP id EFC895FA
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