Bug 1270524 - systemd segfault in timer_enter_waiting while masking a unit
systemd segfault in timer_enter_waiting while masking a unit
Product: Fedora
Classification: Fedora
Component: systemd (Show other bugs)
x86_64 Linux
unspecified Severity medium
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Assigned To: systemd-maint
Fedora Extras Quality Assurance
Depends On:
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Reported: 2015-10-10 11:38 EDT by Sitsofe Wheeler
Modified: 2016-12-20 09:56 EST (History)
4 users (show)

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Doc Type: Bug Fix
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Last Closed: 2016-12-20 09:56:41 EST
Type: Bug
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Description Sitsofe Wheeler 2015-10-10 11:38:03 EDT
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):

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
2. When the system is back up and running log in and run
systemctl edit dnf-makecache.timer
and put the following lines:
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:
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 11:46:19 EDT
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 18:14:19 EST
This one is still here in

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 04:19:15 EST
Filed upstream: https://github.com/systemd/systemd/issues/1981 .
Comment 4 Sitsofe Wheeler 2016-01-09 07:37:35 EST
Changing Fedora version back to 23 per comment #2,
Comment 5 Sitsofe Wheeler 2016-03-01 00:34:27 EST
This is now fixed in systemd v229 by https://github.com/poettering/systemd/commit/e903182e5b0daa941de47a9c08c824106cec7fe0 .
Comment 6 Mike McCune 2016-03-28 19:38:32 EDT
This bug was accidentally moved from POST to MODIFIED via an error in automation, please see mmccune@redhat.com with any questions
Comment 7 Fedora End Of Life 2016-11-24 07:44:50 EST
This message is a reminder that Fedora 23 is nearing its end of life.
Approximately 4 (four) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 23. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
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Comment 8 Fedora End Of Life 2016-12-20 09:56:41 EST
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
security or bug fix updates. As a result we are closing this bug.

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