oops. Thank you for this report and the pointer.

Does this error still occur using 

https://admin.fedoraproject.org/updates/libcap-ng-0.6.6-1.fc15

(In reply to comment #2)
> Does this error still occur using 
> 
> https://admin.fedoraproject.org/updates/libcap-ng-0.6.6-1.fc15

Different header file

 * cap-ng.h vs sys/capability.h

and different library

 * libcap-ng.so vs libcap.so


and syslog-ng's configure only looks for the header file sys/capability.h and the library -lcap.

ok, understood. Should be related to

https://bugzilla.redhat.com/show_bug.cgi?id=689752

right?

Libcap v2.22 is already available for Fedora 15 in the updates repository.

How to reproduce the kernel trace:

System:
VM with Fedora 15 x86_64 (and fully updated)

Packages:
kernel-2.6.40-4.fc15.x86_64
systemd-26-8.fc15.x86_64
libcap-2.22-1.fc15.x86_64
rsyslog-5.8.2-1.fc15.x86_64
syslog-ng-3.2.4-6.fc15.x86_64  (from updates-testing)

Steps:
1) boot vm with rsyslog as the running syslog daemon
2) systemctl disable rsyslog.service;
3) systemctl enable syslog-ng.service
4) systemctl stop rsyslog.service
5) systemctl start syslog-ng.service
6) see kernel trace in /var/log/messages

Trace
--------------------
Aug  7 02:50:53 localhost rsyslogd: [origin software="rsyslogd" swVersion="5.8.2" x-pid="690" x-info="http://www.rsyslog.com"] exiting on signal 15.
Aug  7 02:50:53 localhost kernel: : [  251.396893] ------------[ cut here ]------------
Aug  7 02:50:53 localhost kernel: : [  251.396902] WARNING: at kernel/printk.c:322 do_syslog+0x8e/0x45a()
Aug  7 02:50:53 localhost kernel: : [  251.396935] Hardware name: VMware Virtual Platform
Aug  7 02:50:53 localhost kernel: : [  251.396936] Attempt to access syslog with CAP_SYS_ADMIN but no CAP_SYSLOG (deprecated).
Aug  7 02:50:53 localhost kernel: : [  251.396938] Modules linked in: sunrpc bnep bluetooth rfkill ip6t_REJECT nf_conntrack_ipv4 nf_conntrack_ipv6 nf_defrag_ipv4 nf_defrag_ipv6 ip6table_filter xt_state nf_conntrack ip6_tables snd_ens1371 gameport snd_rawmidi snd_ac97_codec ac97_bus snd_seq snd_seq_device snd_pcm ppdev microcode vmw_balloon snd_timer parport_pc snd i2c_piix4 parport soundcore shpchp snd_page_alloc e1000 i2c_core mptspi mptscsih mptbase scsi_transport_spi [last unloaded: speedstep_lib]
Aug  7 02:50:53 localhost kernel: : [  251.396963] Pid: 1192, comm: syslog-ng Not tainted 2.6.40-4.fc15.x86_64 #1
Aug  7 02:50:53 localhost kernel: : [  251.396965] Call Trace:
Aug  7 02:50:53 localhost kernel: : [  251.396969]  [<ffffffff81054c8e>] warn_slowpath_common+0x83/0x9b
Aug  7 02:50:53 localhost kernel: : [  251.396972]  [<ffffffff81054d49>] warn_slowpath_fmt+0x46/0x48
Aug  7 02:50:53 localhost kernel: : [  251.396976]  [<ffffffff8105e5bd>] ? ns_capable+0x3a/0x4f
Aug  7 02:50:53 localhost syslog-ng[1192]: syslog-ng starting up; version='3.2.4'
Aug  7 02:50:53 localhost kernel: : [  251.396978]  [<ffffffff8105537e>] do_syslog+0x8e/0x45a
Aug  7 02:50:53 localhost kernel: : [  251.396982]  [<ffffffff81171a1e>] ? proc_reg_open+0x41/0x122
Aug  7 02:50:53 localhost kernel: : [  251.396985]  [<ffffffff8111663f>] ? kmem_cache_alloc_trace+0xc6/0xd8
Aug  7 02:50:53 localhost kernel: : [  251.396988]  [<ffffffff8117b5cd>] kmsg_open+0x1c/0x1e
Aug  7 02:50:53 localhost kernel: : [  251.396990]  [<ffffffff81171a84>] proc_reg_open+0xa7/0x122
Aug  7 02:50:53 localhost kernel: : [  251.396992]  [<ffffffff8117b594>] ? read_vmcore+0x1cc/0x1cc
Aug  7 02:50:53 localhost kernel: : [  251.396995]  [<ffffffff811719dd>] ? proc_alloc_inode+0xa1/0xa1
Aug  7 02:50:53 localhost kernel: : [  251.396998]  [<ffffffff81125405>] __dentry_open+0x17d/0x2be
Aug  7 02:50:53 localhost kernel: : [  251.397006]  [<ffffffff814b6fe6>] ? _raw_spin_lock+0xe/0x10
Aug  7 02:50:53 localhost kernel: : [  251.397008]  [<ffffffff8112638f>] nameidata_to_filp+0x60/0x67
Aug  7 02:50:53 localhost kernel: : [  251.397011]  [<ffffffff81131b2a>] do_last+0x434/0x581
Aug  7 02:50:53 localhost kernel: : [  251.397013]  [<ffffffff811327fc>] path_openat+0xc8/0x31c
Aug  7 02:50:53 localhost kernel: : [  251.397016]  [<ffffffff810b2135>] ? __call_rcu+0x130/0x139
Aug  7 02:50:53 localhost kernel: : [  251.397018]  [<ffffffff81132a88>] do_filp_open+0x38/0x86
Aug  7 02:50:53 localhost kernel: : [  251.397021]  [<ffffffff8113c341>] ? alloc_fd+0x72/0x11d
Aug  7 02:50:53 localhost kernel: : [  251.397023]  [<ffffffff81126404>] do_sys_open+0x6e/0x100
Aug  7 02:50:53 localhost kernel: : [  251.397025]  [<ffffffff810a0c7c>] ? audit_syscall_entry+0x145/0x171
Aug  7 02:50:53 localhost kernel: : [  251.397027]  [<ffffffff811264b6>] sys_open+0x20/0x22
Aug  7 02:50:53 localhost kernel: : [  251.397029]  [<ffffffff814bd7c2>] system_call_fastpath+0x16/0x1b
Aug  7 02:50:53 localhost kernel: : [  251.397031] ---[ end trace ac416a71ae31ead5 ]---
--------------------

Additional comments:

 * syslog-ng appears to be working; at least it is running and logs messages
   produced by the logger utility

 * the kernel trace doesn't occur during the following operations
   (ordered):

   1) systemctl stop syslog-ng.service; systemctl start rsyslog.service
   2) logger test1
   3) systemctl stop rsyslog.service; systemctl start syslog-ng.service
   4) logger test2

   But rsyslog doesn't appear to be working correctly as the log message
   from the second operation doesn't get to the /var/log/messages file
   ( but the one from 4) does).

 * a syslog-ng 3.2.4 compiled with capabilities and the upstream patch 
   http://git.balabit.hu/?p=bazsi/syslog-ng-3.2.git;a=commit;h=ae0ff59d9a761c2fda8a19b0c05e0e05c59bae57
   doesn't even start.

Could someone also test this?

Thanks in advance,
jpo

Syslog-ng 3.2.4 with the upstream patch:

 * http://um-pe09-2.di.uminho.pt/fedora/15/syslog-ng-3.2.4-6.2.fc15.src.rpm

Contents diff from syslog-ng-3.2.4-6.fc15.src.rpm:

 * http://um-pe09-2.di.uminho.pt/fedora/15/diff.txt

This message is a notice that Fedora 15 is now at end of life. Fedora 
has stopped maintaining and issuing updates for Fedora 15. It is 
Fedora's policy to close all bug reports from releases that are no 
longer maintained.  At this time, all open bugs with a Fedora 'version'
of '15' have been closed as WONTFIX.

(Please note: Our normal process is to give advanced warning of this 
occurring, but we forgot to do that. A thousand apologies.)

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, feel free to reopen 
this bug and simply change the 'version' to a later Fedora version.

Bug Reporter: Thank you for reporting this issue and we are sorry that 
we were unable to fix it before Fedora 15 reached end of life. If you 
would still like to see this bug fixed and are able to reproduce it 
against a later version of Fedora, you are encouraged to click on 
"Clone This Bug" (top right of this page) and open it against that 
version of Fedora.

Although we aim to fix as many bugs as possible during every release's 
lifetime, sometimes those efforts are overtaken by events.  Often a 
more recent Fedora release includes newer upstream software that fixes 
bugs or makes them obsolete.

The process we are following is described here: 
http://fedoraproject.org/wiki/BugZappers/HouseKeeping

This message is a notice that Fedora 15 is now at end of life. Fedora 
has stopped maintaining and issuing updates for Fedora 15. It is 
Fedora's policy to close all bug reports from releases that are no 
longer maintained.  At this time, all open bugs with a Fedora 'version'
of '15' have been closed as WONTFIX.

(Please note: Our normal process is to give advanced warning of this 
occurring, but we forgot to do that. A thousand apologies.)

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, feel free to reopen 
this bug and simply change the 'version' to a later Fedora version.

Bug Reporter: Thank you for reporting this issue and we are sorry that 
we were unable to fix it before Fedora 15 reached end of life. If you 
would still like to see this bug fixed and are able to reproduce it 
against a later version of Fedora, you are encouraged to click on 
"Clone This Bug" (top right of this page) and open it against that 
version of Fedora.

Although we aim to fix as many bugs as possible during every release's 
lifetime, sometimes those efforts are overtaken by events.  Often a 
more recent Fedora release includes newer upstream software that fixes 
bugs or makes them obsolete.

The process we are following is described here: 
http://fedoraproject.org/wiki/BugZappers/HouseKeeping