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From 096cfb2903d48b115e417010767388ff5c49b282 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Tue, 23 May 2023 06:36:44 +0900
Subject: [PATCH] core/unit: make JoinsNamespaceOf= implies the inverse
dependency
Previously, even if a.service has JoinsNamespaceOf=b.service, the
inverse direction of reference was not introduced.
Hence, a.service is started earlier than b.service, the namespace will
not shared with b.service.
Also, even if a.service had the reference to b.service, b.service did not.
If b.service is freed earlier, then unit_clear_dependencies() does not clear
the reference from a to b, and will cause use-after-free on unit_free() for
a.service.
Let's make JoinsNamespaceOf=b.service in a.service implies the inverse
dependency, i.e. JoinsNamespaceOf=a.service for b.service. Then, we can safely
free b.service.
(cherry picked from commit a60f96fcf55c3452e5b13d6daec537af1909eda3)
Related: #2213521
---
man/systemd.unit.xml | 12 +++++++-----
src/core/unit.c | 11 +++++------
.../testsuite-23-joins-namespace-of-5.service | 2 +-
.../testsuite-23-joins-namespace-of-8.service | 2 +-
.../testsuite-23-joins-namespace-of-9.service | 2 +-
5 files changed, 15 insertions(+), 14 deletions(-)
diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index 8e1a3464df..d41909bcc6 100644
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -858,16 +858,18 @@
<term><varname>JoinsNamespaceOf=</varname></term>
<listitem><para>For units that start processes (such as service units), lists one or more other units
- whose network and/or temporary file namespace to join. This only applies to unit types which support
- the <varname>PrivateNetwork=</varname>, <varname>NetworkNamespacePath=</varname>,
+ whose network and/or temporary file namespace to join. If this is specified on a unit (say, a.service
+ has <varname>JoinsNamespaceOf=b.service</varname>), then this the inverse dependency
+ (<varname>JoinsNamespaceOf=a.service</varname> for b.service) is implied. This only applies to unit
+ types which support the <varname>PrivateNetwork=</varname>, <varname>NetworkNamespacePath=</varname>,
<varname>PrivateIPC=</varname>, <varname>IPCNamespacePath=</varname>, and
<varname>PrivateTmp=</varname> directives (see
<citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
details). If a unit that has this setting set is started, its processes will see the same
<filename>/tmp/</filename>, <filename>/var/tmp/</filename>, IPC namespace and network namespace as
- one listed unit that is started. If multiple listed units are already started, it is not defined
- which namespace is joined. Note that this setting only has an effect if
- <varname>PrivateNetwork=</varname>/<varname>NetworkNamespacePath=</varname>,
+ one listed unit that is started. If multiple listed units are already started and these do not share
+ their namespace, then it is not defined which namespace is joined. Note that this setting only has an
+ effect if <varname>PrivateNetwork=</varname>/<varname>NetworkNamespacePath=</varname>,
<varname>PrivateIPC=</varname>/<varname>IPCNamespacePath=</varname> and/or
<varname>PrivateTmp=</varname> is enabled for both the unit that joins the namespace and the unit
whose namespace is joined.</para></listitem>
diff --git a/src/core/unit.c b/src/core/unit.c
index 0faf66413b..8b66139ad9 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -3108,12 +3108,11 @@ int unit_add_dependency(
return r;
notify = r > 0;
- if (inverse_table[d] != _UNIT_DEPENDENCY_INVALID && inverse_table[d] != d) {
- r = unit_add_dependency_hashmap(&other->dependencies, inverse_table[d], u, 0, mask);
- if (r < 0)
- return r;
- notify_other = r > 0;
- }
+ assert(inverse_table[d] >= 0 && inverse_table[d] < _UNIT_DEPENDENCY_MAX);
+ r = unit_add_dependency_hashmap(&other->dependencies, inverse_table[d], u, 0, mask);
+ if (r < 0)
+ return r;
+ notify_other = r > 0;
if (add_reference) {
r = unit_add_dependency_hashmap(&u->dependencies, UNIT_REFERENCES, other, mask, 0);
diff --git a/test/testsuite-23.units/testsuite-23-joins-namespace-of-5.service b/test/testsuite-23.units/testsuite-23-joins-namespace-of-5.service
index 80594ccba2..c3d316bfa2 100644
--- a/test/testsuite-23.units/testsuite-23-joins-namespace-of-5.service
+++ b/test/testsuite-23.units/testsuite-23-joins-namespace-of-5.service
@@ -3,4 +3,4 @@
Type=oneshot
MountAPIVFS=yes
PrivateTmp=yes
-ExecStart=test ! -e /tmp/shared-private-file
+ExecStart=test -e /tmp/shared-private-file
diff --git a/test/testsuite-23.units/testsuite-23-joins-namespace-of-8.service b/test/testsuite-23.units/testsuite-23-joins-namespace-of-8.service
index f3ec0668de..42053b99f8 100644
--- a/test/testsuite-23.units/testsuite-23-joins-namespace-of-8.service
+++ b/test/testsuite-23.units/testsuite-23-joins-namespace-of-8.service
@@ -4,6 +4,6 @@ Type=notify
NotifyAccess=all
MountAPIVFS=yes
PrivateTmp=yes
-ExecStartPre=test ! -e /tmp/shared-private-file-x
+ExecStartPre=test -e /tmp/shared-private-file-x
ExecStartPre=test ! -e /tmp/hoge
ExecStart=/bin/bash -c 'touch /tmp/shared-private-file-y && systemd-notify --ready && sleep infinity'
diff --git a/test/testsuite-23.units/testsuite-23-joins-namespace-of-9.service b/test/testsuite-23.units/testsuite-23-joins-namespace-of-9.service
index 01de7f9054..a50a7fcdc2 100644
--- a/test/testsuite-23.units/testsuite-23-joins-namespace-of-9.service
+++ b/test/testsuite-23.units/testsuite-23-joins-namespace-of-9.service
@@ -7,5 +7,5 @@ Type=oneshot
MountAPIVFS=yes
PrivateTmp=yes
ExecStart=test ! -e /tmp/shared-private-file-x
-ExecStart=test -e /tmp/shared-private-file-y
+ExecStart=test ! -e /tmp/shared-private-file-y
ExecStart=test ! -e /tmp/hoge
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