shared/install: correctly install alias for units outside search path

Currently, if a unit file is enabled from outside of the search path,
and that unit has an alias, then the symlink ends up pointing outside of
the search path too. For example:

 $ cat /tmp/a.service
 [Service]
 ExecStart=sleep infinity

 [Install]
 Alias=b.service
 WantedBy=multi-user.target

 $ systemctl enable /tmp/a.service
 Created symlink /etc/systemd/system/a.service → /tmp/a.service.
 Created symlink /etc/systemd/system/b.service → /tmp/a.service.
 Created symlink /etc/systemd/system/multi-user.target.wants/a.service → /tmp/a.service.

This then means the alias is treated as a separate unit:

 $ systemctl start a.service
 $ sudo systemctl status a
 ● a.service
  Loaded: loaded (/etc/systemd/system/a.service; enabled; preset: enabled)
  Active: active (running) since Fri 2024-03-15 15:17:49 EDT; 9s ago
 Main PID: 769593 (sleep)
   Tasks: 1 (limit: 18898)
  Memory: 220.0K
     CPU: 5ms
  CGroup: /system.slice/a.service
          └─769593 sleep infinity

 Mar 15 15:17:49 six systemd[1]: Started a.service.
 $ sudo systemctl status b
 ○ b.service
  Loaded: loaded (/etc/systemd/system/b.service; alias)
  Active: inactive (dead)

To fix this, make sure the alias uses a target that is inside the search
path. Since the unit file itself is outside of the search path, a
symlink inside the search path will have been created already. Hence,
just point the alias symlink to that recently created symlink.

diff --git a/src/shared/install.c b/src/shared/install.c
index 81f898f28a477b07df9e33df97857e6ee59867cb..12bf083a2e60d625ed24eb03d35547ceeb64739e 100644 (file)
--- a/src/shared/install.c
+++ b/src/shared/install.c
@@ -1941,7 +1941,7 @@ static int install_info_symlink_alias(
         assert(config_path);
 
         STRV_FOREACH(s, info->aliases) {
-                _cleanup_free_ char *alias_path = NULL, *dst = NULL, *dst_updated = NULL;
+                _cleanup_free_ char *alias_path = NULL, *alias_target = NULL, *dst = NULL, *dst_updated = NULL;
 
                 r = install_name_printf(scope, info, *s, &dst);
                 if (r < 0) {
@@ -1960,6 +1960,18 @@ static int install_info_symlink_alias(
                 if (!alias_path)
                         return -ENOMEM;
 
+                r = in_search_path(lp, info->path);
+                if (r < 0)
+                        return r;
+                if (r == 0) {
+                        /* The unit path itself is outside of the search path. To
+                         * correctly apply the alias, we need the alias symlink to
+                         * point to the symlink that was created in the search path. */
+                        alias_target = path_join(config_path, info->name);
+                        if (!alias_target)
+                                return -ENOMEM;
+                }
+
                 bool broken;
                 r = chase(alias_path, lp->root_dir, CHASE_NONEXISTENT, /* ret_path = */ NULL, /* ret_fd = */ NULL);
                 if (r < 0 && r != -ENOENT) {
@@ -1968,7 +1980,7 @@ static int install_info_symlink_alias(
                 }
                 broken = r == 0; /* symlink target does not exist? */
 
-                RET_GATHER(ret, create_symlink(lp, info->path, alias_path, force || broken, changes, n_changes));
+                RET_GATHER(ret, create_symlink(lp, alias_target ?: info->path, alias_path, force || broken, changes, n_changes));
         }
 
         return ret;

diff --git a/src/test/test-install-root.c b/src/test/test-install-root.c
index efd75b2a6798b70205d5bea42e697b572ffc2f46..c55445079c6c6fc62f19033c4966074b629d2a40 100644 (file)
--- a/src/test/test-install-root.c
+++ b/src/test/test-install-root.c
@@ -200,7 +200,7 @@ TEST(basic_mask_and_enable) {
 }
 
 TEST(linked_units) {
-        const char *p, *q;
+        const char *p, *q, *s;
         UnitFileState state;
         InstallChange *changes = NULL;
         size_t n_changes = 0, i;
@@ -224,6 +224,7 @@ TEST(linked_units) {
         p = strjoina(root, "/opt/linked.service");
         assert_se(write_string_file(p,
                                     "[Install]\n"
+                                    "Alias=linked-alias.service\n"
                                     "WantedBy=multi-user.target\n", WRITE_STRING_FILE_CREATE) >= 0);
 
         p = strjoina(root, "/opt/linked2.service");
@@ -275,31 +276,41 @@ TEST(linked_units) {
 
         /* Now, let's not just link it, but also enable it */
         assert_se(unit_file_enable(RUNTIME_SCOPE_SYSTEM, 0, root, STRV_MAKE("/opt/linked.service"), &changes, &n_changes) >= 0);
-        assert_se(n_changes == 2);
+        assert_se(n_changes == 3);
         p = strjoina(root, SYSTEM_CONFIG_UNIT_DIR"/multi-user.target.wants/linked.service");
         q = strjoina(root, SYSTEM_CONFIG_UNIT_DIR"/linked.service");
+        s = strjoina(root, SYSTEM_CONFIG_UNIT_DIR"/linked-alias.service");
         for (i = 0 ; i < n_changes; i++) {
                 assert_se(changes[i].type == INSTALL_CHANGE_SYMLINK);
-                assert_se(streq(changes[i].source, "/opt/linked.service"));
+
+                if (s && streq(changes[i].path, s))
+                        /* The alias symlink should point within the search path. */
+                        assert_se(streq(changes[i].source, SYSTEM_CONFIG_UNIT_DIR"/linked.service"));
+                else
+                        assert_se(streq(changes[i].source, "/opt/linked.service"));
 
                 if (p && streq(changes[i].path, p))
                         p = NULL;
                 else if (q && streq(changes[i].path, q))
                         q = NULL;
+                else if (s && streq(changes[i].path, s))
+                        s = NULL;
                 else
                         assert_not_reached();
         }
-        assert_se(!p && !q);
+        assert_se(!p && !q && !s);
         install_changes_free(changes, n_changes);
         changes = NULL; n_changes = 0;
 
         assert_se(unit_file_get_state(RUNTIME_SCOPE_SYSTEM, root, "linked.service", &state) >= 0 && state == UNIT_FILE_ENABLED);
+        assert_se(unit_file_get_state(RUNTIME_SCOPE_SYSTEM, root, "linked-alias.service", &state) >= 0 && state == UNIT_FILE_ALIAS);
 
         /* And let's unlink it again */
         assert_se(unit_file_disable(RUNTIME_SCOPE_SYSTEM, 0, root, STRV_MAKE("linked.service"), &changes, &n_changes) >= 0);
-        assert_se(n_changes == 2);
+        assert_se(n_changes == 3);
         p = strjoina(root, SYSTEM_CONFIG_UNIT_DIR"/multi-user.target.wants/linked.service");
         q = strjoina(root, SYSTEM_CONFIG_UNIT_DIR"/linked.service");
+        s = strjoina(root, SYSTEM_CONFIG_UNIT_DIR"/linked-alias.service");
         for (i = 0; i < n_changes; i++) {
                 assert_se(changes[i].type == INSTALL_CHANGE_UNLINK);
 
@@ -307,10 +318,12 @@ TEST(linked_units) {
                         p = NULL;
                 else if (q && streq(changes[i].path, q))
                         q = NULL;
+                else if (s && streq(changes[i].path, s))
+                        s = NULL;
                 else
                         assert_not_reached();
         }
-        assert_se(!p && !q);
+        assert_se(!p && !q && !s);
         install_changes_free(changes, n_changes);
         changes = NULL; n_changes = 0;
 

diff --git a/test/test-systemctl-enable.sh b/test/test-systemctl-enable.sh
index 8427f6849bfd9e7921bf9a9a2af40678c9ab1415..5615c900f4861ffa2fe410407a64a2f85573578f 100644 (file)
--- a/test/test-systemctl-enable.sh
+++ b/test/test-systemctl-enable.sh
@@ -534,8 +534,8 @@ test ! -h "$root/etc/systemd/system/link5alias2.service"
 
 "$systemctl" --root="$root" enable '/link5copy.service'
 islink "$root/etc/systemd/system/link5copy.service" '/link5copy.service'
-islink "$root/etc/systemd/system/link5alias.service" '/link5copy.service'
-islink "$root/etc/systemd/system/link5alias2.service" '/link5copy.service'
+islink "$root/etc/systemd/system/link5alias.service" '/etc/systemd/system/link5copy.service'
+islink "$root/etc/systemd/system/link5alias2.service" '/etc/systemd/system/link5copy.service'
 
 "$systemctl" --root="$root" disable 'link5copy.service'
 test ! -h "$root/etc/systemd/system/link5copy.service"