From: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Date: Thu, 13 Feb 2025 14:49:50 +0000 (+0100)
Subject: core/condition: fix segfault when key not found in os-release
X-Git-Tag: v258-rc1~1348
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=de02b551adcf74e5677454fd36bf7653b1a4def1;p=thirdparty%2Fsystemd.git

core/condition: fix segfault when key not found in os-release

'ConditionOSRelease=|ID_LIKE$=*rhel*' results in a segfault.
The key 'ID_LIKE' is not present in Fedora's os-release file.

I think the most reasonable behaviour is to treat missing keys as empty.
This matches the "shell-like" sprit, since in a shell empty keys would
by default be treated as empty too. Thus, "ID_LIKE=" would match, if
ID_LIKE is not present in the file, and ID_LIKE=!$foo" would also match.
The other option would be to make those matches fail, but I think that'd
make the feature harder to use, esp. with negative matches.

Documentation is updated to clarify the new behaviour.

https://bugzilla.redhat.com/show_bug.cgi?id=2345544
---

diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index 44eb51c83a4..62803006086 100644
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -1960,6 +1960,8 @@
           wildcard comparisons (<literal>*</literal>, <literal>?</literal>, <literal>[]</literal>) are
           supported with the <literal>$=</literal> (match) and <literal>!$=</literal> (non-match).</para>
 
+          <para>If the given key is not found in the file, the match is done against an empty value.</para>
+
           <xi:include href="version-info.xml" xpointer="v249"/>
           </listitem>
         </varlistentry>
diff --git a/src/shared/condition.c b/src/shared/condition.c
index 390f9537bbf..c0c656d2e69 100644
--- a/src/shared/condition.c
+++ b/src/shared/condition.c
@@ -275,7 +275,9 @@ static int condition_test_osrelease(Condition *c, char **env) {
                 if (r < 0)
                         return log_debug_errno(r, "Failed to parse os-release: %m");
 
-                r = version_or_fnmatch_compare(operator, actual_value, word);
+                /* If not found, use "". This means that missing and empty assignments
+                 * in the file have the same result. */
+                r = version_or_fnmatch_compare(operator, strempty(actual_value), word);
                 if (r < 0)
                         return r;
                 if (!r)
diff --git a/src/test/test-condition.c b/src/test/test-condition.c
index dcd1aea384c..7e983213500 100644
--- a/src/test/test-condition.c
+++ b/src/test/test-condition.c
@@ -1095,6 +1095,24 @@ TEST(condition_test_os_release) {
         ASSERT_OK_POSITIVE(condition_test(condition, environ));
         condition_free(condition);
 
+        /* Test shell style globs */
+
+        ASSERT_NOT_NULL(condition = condition_new(CONDITION_OS_RELEASE, "ID_LIKE$=*THISHOPEFULLYWONTEXIST*", false, false));
+        ASSERT_OK_ZERO(condition_test(condition, environ));
+        condition_free(condition);
+
+        ASSERT_NOT_NULL(condition = condition_new(CONDITION_OS_RELEASE, "ID_THISHOPEFULLYWONTEXIST$=*rhel*", false, false));
+        ASSERT_OK_ZERO(condition_test(condition, environ));
+        condition_free(condition);
+
+        ASSERT_NOT_NULL(condition = condition_new(CONDITION_OS_RELEASE, "ID_LIKE!$=*THISHOPEFULLYWONTEXIST*", false, false));
+        ASSERT_OK_POSITIVE(condition_test(condition, environ));
+        condition_free(condition);
+
+        ASSERT_NOT_NULL(condition = condition_new(CONDITION_OS_RELEASE, "ID_THISHOPEFULLYWONTEXIST!$=*rhel*", false, false));
+        ASSERT_OK_POSITIVE(condition_test(condition, environ));
+        condition_free(condition);
+
         /* load_os_release_pairs() removes quotes, we have to add them back,
          * otherwise we get a string: "PRETTY_NAME=Debian GNU/Linux 10 (buster)"
          * which is wrong, as the value is not quoted anymore. */