Devuan bug report logs - #929
libfastjson4 linked without -lm causes segfault in rsyslog with libc6 2.42

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Message #5 received at submit@bugs.devuan.org (full text, mbox, reply):

Package: rsyslog
Version: 8.2510.0-5devuan1
Severity: grave
Justification: renders package unusable

Hey,
since upgrading libc6 today, rsyslog fails with following message : 

# /usr/sbin/rsyslogd -n -iNONE
/usr/sbin/rsyslogd: Relink `/usr/lib/x86_64-linux-gnu/libfastjson.so.4' with `/usr/lib/x86_64-linux-gnu/libm.so.6' for IFUNC symbol `modf'
Segmentation fault

dmesg : 
rsyslogd[4291]: segfault at 9c ip 00007fb603e233a7 sp 00007ffe50362148 error 4 in libm.so.6[4b3a7,7fb603de9000+82000] likely on CPU 2 (core 0, socket 0)

after downgrading libc6, libc6-bin, locales to testing version (2.41-12) , rsyslog works again as it should.

thanks,
d.

-- System Information:
Distributor ID:	Devuan
Description:	Devuan GNU/Linux 7 (freia/ceres)
Release:	7
Codename:	freia ceres
Architecture: x86_64

Kernel: Linux 6.17.9+deb14-amd64 (SMP w/4 CPU threads; PREEMPT)
Locale: LANG=el_GR.UTF-8, LC_CTYPE=el_GR.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: runit (via /run/runit.stopit)
LSM: AppArmor: enabled

Versions of packages rsyslog depends on:
ii  init-system-helpers        1.69devuan1
ii  libc6                      2.42-4
ii  libestr0                   0.1.11-2
ii  libfastjson4               1.2304.0-2
ii  liblognorm5                2.0.7-1
ii  libuuid1                   2.41.2-4devuan1
ii  libzstd1                   1.5.7+dfsg-2
ii  lsb-base                   11.6
ii  sysvinit-utils [lsb-base]  3.15-6devuan1
ii  zlib1g                     1:1.3.dfsg+really1.3.1-1+b1

Versions of packages rsyslog recommends:
ii  logrotate  3.22.0-1

Versions of packages rsyslog suggests:
pn  rsyslog-clickhouse                <none>
pn  rsyslog-doc                       <none>
pn  rsyslog-docker                    <none>
pn  rsyslog-elasticsearch             <none>
pn  rsyslog-gssapi                    <none>
pn  rsyslog-hiredis                   <none>
pn  rsyslog-kafka                     <none>
pn  rsyslog-kubernetes                <none>
pn  rsyslog-mongodb                   <none>
pn  rsyslog-mysql                     <none>
pn  rsyslog-openssl | rsyslog-gnutls  <none>
pn  rsyslog-pgsql                     <none>
pn  rsyslog-relp                      <none>
pn  rsyslog-snmp                      <none>

-- Configuration Files:
/etc/logrotate.d/rsyslog [file not found]

-- no debconf information

Message #10 received at 929@bugs.devuan.org (full text, mbox, reply):

hadn't checked older bugs...,

seems to be the same(?)/similar to 
https://bugs.devuan.org/cgi/bugreport.cgi?bug=908


thanks,

d.

Message #13 received at 929@bugs.devuan.org (full text, mbox, reply):

Dimitris

Thanks.

On Thu, Dec 04, 2025 at 02:15:45PM +0200, Dimitris T. wrote:
> Package: rsyslog
> Version: 8.2510.0-5devuan1
> Severity: grave
> Justification: renders package unusable
> 
> Hey,
> since upgrading libc6 today, rsyslog fails with following message : 
> 
> # /usr/sbin/rsyslogd -n -iNONE
> /usr/sbin/rsyslogd: Relink `/usr/lib/x86_64-linux-gnu/libfastjson.so.4' with `/usr/lib/x86_64-linux-gnu/libm.so.6' for IFUNC symbol `modf'
> Segmentation fault

I have to admit to not understanding fully the intricacies of the linking and
symbols here.

There is an apparently equivalent Gentoo bug[1] that suggests this should be
resolved in libfastjson4. In other words it is for Debian to resolve.

Let me do some more research.

Mark

[1]  https://bugs.gentoo.org/961289

Message #16 received at 929@bugs.devuan.org (full text, mbox, reply):

On Thu, Dec 04, 2025 at 02:39:56PM +0200, Dimitris T. wrote:
> hadn't checked older bugs...,
> 
> seems to be the same(?)/similar to
> https://bugs.devuan.org/cgi/bugreport.cgi?bug=908

Yes, maybe my assessment there was incorrect. But the #908 OP didn't say it
wasn't fixed as I thought...

Mark

Message #19 received at 929@bugs.devuan.org (full text, mbox, reply):

Control: reassign -1 libfastjson-dev
Control: retitle -1 libfastjson4 linked without -lm causes segfault in rsyslog with libc6 2.42
Control: tags -1 debian
Control: affects -1 rsyslog
Control: forwarded -1 https://bugs.debian.org/1114612

Dimitris,

The issue appears to be lack of -lm linkage after a change in libc6 modf()
implementation in 2.42. However, it is only triggered in rsyslog builds without
systemd (hence only reports from  Devuan, Gentoo and Artix.)

It is fixed in libfastjson upstream[1]. Src:libfastjson is not forked in Devuan
and I have reopened the existing Debian bug[2] to request the fix be cherry-picked.

Mark

[1]  https://github.com/rsyslog/libfastjson/pull/167

[2]  https://bugs.debian.org/1114612

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