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

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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.
This commit is contained in:
Nick Rosbrook 2024-03-15 15:14:05 -04:00 committed by Luca Boccassi
parent ce88017255
commit 6fec0fed10
3 changed files with 35 additions and 10 deletions
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16
src/shared/install.c
View File

@ -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;

25
src/test/test-install-root.c
View File

@ -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;

4
test/test-systemctl-enable.sh
View File

@ -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"