[systemd-bugs] [Bug 88007] New: Segfault caused by utilities like iptables, netstat-nat and jnettop after upgrading to systemd 218-1 from 216-3

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88007

            Bug ID: 88007
           Summary: Segfault caused by utilities like iptables,
                    netstat-nat and jnettop after upgrading to systemd
                    218-1 from 216-3
           Product: systemd
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: general
          Assignee: systemd-bugs at lists.freedesktop.org
          Reporter: zakoyan at gmail.com
        QA Contact: systemd-bugs at lists.freedesktop.org

I am using ArchLinux on my Linux box router. It serves some 100 of companies
and takes care of BGP announcements of my IP space so I don't upgrade the OS
really often.
After I performed full system upgrade and rebooted the box, I found
sshd.service segfaulting very quickly after being started. The version of
systemd raised from 216-3 to 218-1
I just disabled it and installed dropbear instead, which worked just well.
But soon I noticed segfaults from different programs like 'iptables -L',
'netstat-nat' and 'jnettop'. They all dropped into segfault after exposing
several strings with hostnames.
I tried disabling host name backresolve, and it kind of helped to run 'iptables
-L -n', but both jnettop and netstat-nat still went on segfaulting.

Well, I installed gdb and digged deeper.

After applying some efforts (it was the first time I ever ran gdb) I found that
all the three utils caused the same segfault like this:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7493dd5 in _int_free () from /usr/lib/libc.so.6

'info s' command of gdb gave me the following:

#0  0x00007ffff7493dd5 in _int_free () from /usr/lib/libc.so.6
#1  0x00007ffff7fd734a in ?? () from /usr/lib/libnss_myhostname.so.2
#2  0x00007ffff7fd7377 in ?? () from /usr/lib/libnss_myhostname.so.2
#3  0x00007ffff7fd7377 in ?? () from /usr/lib/libnss_myhostname.so.2
#4  0x00007ffff7fd7377 in ?? () from /usr/lib/libnss_myhostname.so.2
#5  0x00007ffff7fd7377 in ?? () from /usr/lib/libnss_myhostname.so.2

and really lots of last string repeating (>4000)

libnss_myhostname looked like a good prompt; I found the way to disable that
lib calls in /etc/nsswitch.conf by commenting out myhostname in
'hosts: files dns myhostname' ,
and the problem got solved.

Bad thing about reproducing the bug is that a LAMP server I run ArchLinux on
operates just great and happily runs iptables and everything.
But I just have to set back 'myhostname' keyword in /etc/nsswitch.conf to have
the segfaults back on my router box. 
Will be glad to be helpful in eliminating this problem.

Regards, 
Tigran Zakoyan

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