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<base href="https://bugs.freedesktop.org/" />
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<th>Priority</th>
<td>medium
</td>
</tr>
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - dangling symlink in .d drop-in causes systemd to crash"
href="https://bugs.freedesktop.org/show_bug.cgi?id=76899">76899</a>
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<th>Assignee</th>
<td>systemd-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Summary</th>
<td>dangling symlink in .d drop-in causes systemd to crash
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>systemd-bugs@lists.freedesktop.org
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
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<th>Reporter</th>
<td>mbiebl@gmail.com
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<th>Hardware</th>
<td>Other
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Component</th>
<td>general
</td>
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<th>Product</th>
<td>systemd
</td>
</tr></table>
<p>
<div>
<pre>systemd can be crashed by using creating a dangling symlink in foo.service.d/.
It was originally filed in the Debian bug tracker [0].
To trigger the bug, you need a socket activated service. I'm using
cups in this case.
The steps to reproduce are
a/ Make sure cups.socket is properly configured and in state active (listening)
b/ Make sure cups.service is *not* running
c/ Create /etc/systemd/system/cups.socket.conf.d/ and then a dangling
symlink like this ln -s /nonexistent
/etc/systemd/system/cups.socket.conf.d/foo.conf
d/ Run systemctl daemon-reload
The socket is now in this state:
Active: active (listening)
Loaded: error (Reason: No such file or directory)
e/ Now trigger a request on the cups.socket, e.g. using lpq
→ systemd freezes
The problem afaics is triggered in src/core/socket.c:
socket_enter_running(), when the incoming request causes the start of
the corresponding service unit via
r = manager_add_job(UNIT(s)->manager, JOB_START, UNIT_DEREF(s->service),
JOB_REPLACE, true, &error, NULL);
I think after the socket configuration has been messed up and the
daemon-reload, UNIT_DEREF(s->service) does no longer point to a valid
unit, and so the assert in manager_add_job() kicks in.
I tested this with 204 and 208, and both versions are affected.
Any suggestions how to fix this?
A few remarks/questions:
1/ A dangling drop-in snippet should imho *not* cause the unit Load state to be
Loaded: error (Reason: No such file or directory)
2/ If a socket is in such a state, we probably shouldn't process
incoming requests and try to start the service
3/ Should we stop the socket if the Load state is "error"?
[0] <a href="https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=742322#58">https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=742322#58</a></pre>
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