Bug 1651257

Summary:	access to automounted dir with expiration time set can hang
Product:	Red Hat Enterprise Linux 7	Reporter:	David Tardon <dtardon>
Component:	systemd	Assignee:	David Tardon <dtardon>
Status:	CLOSED ERRATA	QA Contact:	Frantisek Sumsal <fsumsal>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	7.5	CC:	dtardon, myllynen, single_08, systemd-maint-list
Target Milestone:	rc
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Hardware:	Unspecified
OS:	Unspecified
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Fixed In Version:	systemd-219-64.el7	Doc Type:	If docs needed, set a value
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Last Closed:	2019-08-06 12:43:36 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Description David Tardon 2018-11-19 14:41:10 UTC

Description of problem:
If an expiration time is set for an automount unit, an access to the automounted dir after it expired will hang if 'systemd daemon-reload' was run meanwhile.

Version-Release number of selected component (if applicable):
systemd-219.57.el7

How reproducible:
always

Steps to Reproduce:
# Setup
1. mkdir /etc/systemd/system/proc-sys-fs-binfmt_misc.automount.d
2. echo -e "[Automount]\nTimeoutIdleSec=5s" > /etc/systemd/system/proc-sys-fs-binfmt_misc.automount.d/timeout.conf # set up expiration time
3. systemctl daemon-reload # load the new config
4. systemctl restart proc-sys-fs-binfmt_misc.automount # optional, just to be sure
5. ls /proc/sys/fs/binfmt_misc # trigger the automount
6. sleep 5 # now let it expire
7. systemctl daemon-reload # trigger the bug
8. ls /proc/sys/fs/binfmt_misc # hang

Actual results:
ls hangs.

Expected results:
ls shows the content of the dir.

Additional info:
This is a regression in systemd-219-59 (7.5), caused by patch 0561-automount-if-an-automount-unit-is-masked-don-t-react.patch .

The bug can manifest itself during update from 7.3 to 7.5/7.6 (but not from 7.4 to 7.5), because systemd-219-30 in 7.3 hardcodes expiration timeout to 5min (expiration is disabled by default from 7.4 up). However, systemd-219-30 doesn't actually handle expiration. That was only fixed in systemd-219-42 in 7.4. And there is a lot of daemon-reloads run during the update.

Comment 2 David Tardon 2018-11-19 15:34:18 UTC

https://github.com/lnykryn/systemd-rhel/pull/243

Comment 3 kevin 2018-11-21 02:37:30 UTC

hello, 
what about 7.2? my issue happened in 7.2 with 'systemd-219-19.el7.x86_64' installed. I also did the steps to reproduce, but it didnt work on 7.2.

additional info:
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=29,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)

Thanks!

Comment 4 David Tardon 2018-11-21 08:59:10 UTC

(In reply to kevin from comment #3)
> hello, 
> what about 7.2? my issue happened in 7.2 with 'systemd-219-19.el7.x86_64'
> installed. I also did the steps to reproduce, but it didnt work on 7.2.

systemd didn't even handle automount expiration before 7.4. And the patch that causes this bug was added in 7.5. So whatever problem you have, it's something different than this.

Comment 6 Lukáš Nykrýn 2019-02-11 09:43:25 UTC

fix merged to staging branch -> https://github.com/lnykryn/systemd-rhel/pull/243 -> post

Comment 10 errata-xmlrpc 2019-08-06 12:43:36 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2019:2091