[Dnsmasq-discuss] crash on double free

Ferenc Wagner wferi at niif.hu
Tue Sep 14 15:12:48 BST 2010

Ferenc Wagner <wferi at niif.hu> writes:

> *** glibc detected *** /usr/sbin/dnsmasq: double free or corruption (top): 0x08ab60b8 ***
> [...]
> I've got the core file, but no debugging info.  The binary is the Debian
> Squeeze one from dnsmasq-base_2.55-1_i386.deb, running on a Lenny
> system...  I decided to still report this, because I don't think mixing
> in this package from another distribution should matter.  Maybe I'm wrong.
> It's a pity dnsmasq-core-dbg does not exist.  Tomorrow I'll probably get
> a chance to rebuild the package with debugging info.

I rebuilt the 2.55-1 source package under Lenny with debug info, and
reproduced the crash.  The backtrace is somewhat broken (address
0x2b07\n?!), but maybe still useful:

$ gdb dnsmasq core
GNU gdb 6.8-debian
Core was generated by `/usr/sbin/dnsmasq -d -x /var/run/dnsmasq/dnsmasq.pid -u dnsmasq -7 /etc/dnsmasq'.
Program terminated with signal 6, Aborted.
(gdb) bt
#0  0xb7719416 in __kernel_vsyscall ()
#1  0xb7578640 in raise () from /lib/i686/cmov/libc.so.6
#2  0xb757a018 in abort () from /lib/i686/cmov/libc.so.6
#3  0xb75b548d in __libc_message () from /lib/i686/cmov/libc.so.6
#4  0xb75bb764 in malloc_printerr () from /lib/i686/cmov/libc.so.6
#5  0xb75bd966 in free () from /lib/i686/cmov/libc.so.6
#6  0x08060346 in do_script_run (now=1284470981) at lease.c:602
#7  0x0805d047 in main (argc=Cannot access memory at address 0x2b07
) at dnsmasq.c:617

I'll try to link in efence, and hope for a better report.

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