Bug 1270524

Summary:	systemd segfault in timer_enter_waiting while masking a unit
Product:	[Fedora] Fedora	Reporter:	Sitsofe Wheeler <sitsofe>
Component:	systemd	Assignee:	systemd-maint
Status:	CLOSED EOL	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	23	CC:	jsynacek, lnykryn, msekleta, systemd-maint
Target Milestone:	---
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-12-20 14:56:41 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Sitsofe Wheeler 2015-10-10 15:38:03 UTC

Description of problem:
While trying to mask a timer file that in turn has a subunit override systemd segfaulted.

Version-Release number of selected component (if applicable):
systemd-219-24.fc22.x86_64

How reproducible:
Reproducible every time.

Steps to Reproduce:
1. Run
rm /etc/systemd/system/dnf-makecache.timer.d/override.conf
systemctl unmask dnf-makecache.timer
reboot
.
2. When the system is back up and running log in and run
systemctl edit dnf-makecache.timer
and put the following lines:
[Timer]
OnBootSec=10s
OnUnitInactiveSec=1h
and then save and quit your editor.
3. Run
systemctl mask dnf-makecache.timer
.

Actual results:
The following is printed:
Broadcast message from systemd-journald@<hostname> (Sat 2015-10-10 15:31:20 UTC):

systemd[1]: Caught <SEGV>, dumped core as pid 819.


Broadcast message from systemd-journald@<hostname> (Sat 2015-10-10 15:31:20 UTC):

systemd[1]: Freezing execution.

and it is no longer possible to start/stop systemd units or change runlevels/reboot cleanly.

Expected results:
dnf-makecache.timer unit to be masked out?

Additional info:
Using
echo "/tmp/core" > /proc/sys/kernel/core_pattern
before step 3 allows a core dump to be produced. Looking at the backtrace in the coredump shows the following:
#0  0x00007f433b062d07 in kill () from /lib64/libc.so.6
#1  0x0000563ce32c04dd in crash.lto_priv ()
#2  <signal handler called>
#3  0x0000563ce337240c in timer_enter_waiting ()
#4  0x0000563ce3372d7d in timer_enter_waiting_coldplug ()
#5  0x0000563ce3386226 in manager_coldplug.lto_priv ()
#6  0x0000563ce32b8ef4 in manager_reload ()
#7  0x0000563ce32bb819 in main ()

systemd-219-20 seems to segfault with the same steps. I don't think this is security sensitive because I would imagine normal users would only crash their own systemd using these steps rather than the system one but I'll mark this private and someone can make it publically viewable after reviewing it.

Comment 1 Sitsofe Wheeler 2015-10-10 15:46:19 UTC

dmesg also contains the following:
[   49.866897] systemd[1]: segfault at 1d0 ip 0000556629ef640c sp 00007ffffa39f700 error 4 in systemd[556629e1b000+14a000]
[   49.882635] systemd-coredum[820]: segfault at 0 ip 0000561607fb4361 sp 00007ffe6effbc90 error 6 in systemd-coredump[561607fa6000+18000]

Comment 2 Sitsofe Wheeler 2015-11-14 23:14:19 UTC

This one is still here in
systemd-222-8.fc23.x86_64

Can we make this issue public as I don't think anyone is going to look at it otherwise...

Comment 3 Sitsofe Wheeler 2015-11-22 09:19:15 UTC

Filed upstream: https://github.com/systemd/systemd/issues/1981 .

Comment 4 Sitsofe Wheeler 2016-01-09 12:37:35 UTC

Changing Fedora version back to 23 per comment #2,

Comment 5 Sitsofe Wheeler 2016-03-01 05:34:27 UTC

This is now fixed in systemd v229 by https://github.com/poettering/systemd/commit/e903182e5b0daa941de47a9c08c824106cec7fe0 .

Comment 6 Mike McCune 2016-03-28 23:38:32 UTC

This bug was accidentally moved from POST to MODIFIED via an error in automation, please see mmccune with any questions

Comment 7 Fedora End Of Life 2016-11-24 12:44:50 UTC

This message is a reminder that Fedora 23 is nearing its end of life.
Approximately 4 (four) weeks from now Fedora will stop maintaining
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Comment 8 Fedora End Of Life 2016-12-20 14:56:41 UTC

Fedora 23 changed to end-of-life (EOL) status on 2016-12-20. Fedora 23 is
no longer maintained, which means that it will not receive any further
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