[Dnsmasq-discuss] dnsmasq rc5 segfault

[Simon Kelley]

Carlos Carvalho wrote:
> Simon Kelley (simon at thekelleys.org.uk) wrote on 11 July 2008 19:40:
>  >Carlos Carvalho wrote:
>  >> Today dnsmasq died. It was the first time since I use it :-(
>  >> 
>  >> In its log there's no sign of problems. The last entry is for a
>  >> DHCPNAK; it's the only such record with 2.43. The kernel log says
>  >> 
>  >> Jul 11 14:27:38 hoggar dnsmasq[11797]: segfault at 10 ip 08061e91 sp bfffe770 error 4 in dnsmasq[8048000+22000]
>  >> 
>  >> The kernel is compiled with several PAX protections, in particular
>  >> non-executable pages.
>  >> 
>  >> Any ideas on how to debug this? All I can imagine demand a significant
>  >> amount of work here :-(
>  >> 
>  >
>  >Best bet is to be ready to catch the next one.
>  >
>  >1) rebuild dnsmasq with
>  >
>  >make CFLAGS=-g
> 
> Done.
> 
>  >2) enable coredumps and move to a directory where they can be written
>  >
>  >ulimit -c unlimited
> 
> Done.
> 
>  >3) run dnsmasq in the foreground
>  >
>  >dnsmasq -d
> 
> D... ops, sorry, I can't run a segfaulting program as root in the
> central server of the department...
> 
> I ran it normally and sent it a quit signal but it didn't produce a
> core; it works for other programs. I changed the chdir / in dnsmasq.c
> to "/tmp" to no avail (it does the chdir). Why doesn't it produce a core?
> 
If you're changing code, try making

   if (daemon->options & OPT_DEBUG)
     prctl(PR_SET_DUMPABLE, 1);

in dnsmasq.c

unconditional

Cheers

Simon.