cgroup: always validate cgroup controller names

Let's better be safe than sorry.

TODO

@@ -57,10 +57,6 @@ Features:
 
 * add s.th. like "systemctl set-log-level debug"
 
-* sd-login: allow enumerating machines and add inotify iface
-
-* cgroup-util: verify syntax of cgroup controllers
-
 * cgtop: make cgtop useful in a container
 
 * make sure cg_pid_get_path() works properly for co-mounted controllers

src/core/unit.c

@@ -1938,7 +1938,7 @@ char *unit_dbus_path(Unit *u) {
         return unit_dbus_path_from_name(u->id);
 }
 
-int unit_add_cgroup(Unit *u, CGroupBonding *b) {
+static int unit_add_cgroup(Unit *u, CGroupBonding *b) {
         int r;
 
         assert(u);
@@ -2100,6 +2100,9 @@ static int unit_add_one_default_cgroup(Unit *u, const char *controller) {
 
         assert(u);
 
+        if (controller && !cg_controller_is_valid(controller, true))
+                return -EINVAL;
+
         if (!controller)
                 controller = SYSTEMD_CGROUP_CONTROLLER;
 
@@ -2202,13 +2205,15 @@ int unit_add_cgroup_attribute(
                 controller = c;
         }
 
-        if (!controller || streq(controller, SYSTEMD_CGROUP_CONTROLLER))
+        if (!controller ||
+            streq(controller, SYSTEMD_CGROUP_CONTROLLER) ||
+            streq(controller, "systemd"))
                 return -EINVAL;
 
         if (!filename_is_safe(name))
                 return -EINVAL;
 
-        if (!filename_is_safe(controller))
+        if (!cg_controller_is_valid(controller, false))
                 return -EINVAL;
 
         /* Check if this attribute already exists. Note that we will
@@ -2276,42 +2281,39 @@ int unit_add_cgroup_attribute(
 }
 
 int unit_load_related_unit(Unit *u, const char *type, Unit **_found) {
-        char *t;
+        _cleanup_free_ char *t = NULL;
         int r;
 
         assert(u);
         assert(type);
         assert(_found);
 
-        if (!(t = unit_name_change_suffix(u->id, type)))
+        t = unit_name_change_suffix(u->id, type);
+        if (!t)
                 return -ENOMEM;
 
         assert(!unit_has_name(u, t));
 
         r = manager_load_unit(u->manager, t, NULL, NULL, _found);
-        free(t);
-
         assert(r < 0 || *_found != u);
-
         return r;
 }
 
 int unit_get_related_unit(Unit *u, const char *type, Unit **_found) {
+        _cleanup_free_ char *t = NULL;
         Unit *found;
-        char *t;
 
         assert(u);
         assert(type);
         assert(_found);
 
-        if (!(t = unit_name_change_suffix(u->id, type)))
+        t = unit_name_change_suffix(u->id, type);
+        if (!t)
                 return -ENOMEM;
 
         assert(!unit_has_name(u, t));
 
         found = manager_get_unit(u->manager, t);
-        free(t);
-
         if (!found)
                 return -ENOENT;
 

src/core/unit.h

@@ -450,7 +450,6 @@ int unit_add_two_dependencies_by_name_inverse(Unit *u, UnitDependency d, UnitDep
 
 int unit_add_exec_dependencies(Unit *u, ExecContext *c);
 
-int unit_add_cgroup(Unit *u, CGroupBonding *b);
 int unit_add_cgroup_from_text(Unit *u, const char *name, bool overwrite, CGroupBonding **ret);
 int unit_add_default_cgroups(Unit *u);
 CGroupBonding* unit_get_default_cgroup(Unit *u);

src/shared/cgroup-util.c

@@ -510,6 +510,9 @@ int cg_get_path(const char *controller, const char *path, const char *suffix, ch
 
         assert(fs);
 
+        if (controller && !cg_controller_is_valid(controller, true))
+                return -EINVAL;
+
         if (_unlikely_(!good)) {
                 int r;
 
@@ -546,7 +549,7 @@ int cg_get_path_and_check(const char *controller, const char *path, const char *
 
         assert(fs);
 
-        if (isempty(controller))
+        if (!cg_controller_is_valid(controller, true))
                 return -EINVAL;
 
         /* Normalize the controller syntax */
@@ -741,6 +744,9 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path) {
         assert(path);
         assert(pid >= 0);
 
+        if (controller && !cg_controller_is_valid(controller, true))
+                return -EINVAL;
+
         if (!controller)
                 controller = SYSTEMD_CGROUP_CONTROLLER;
 
@@ -933,7 +939,7 @@ int cg_split_spec(const char *spec, char **controller, char **path) {
 
         e = strchr(spec, ':');
         if (!e) {
-                if (!filename_is_safe(spec))
+                if (!cg_controller_is_valid(spec, true))
                         return -EINVAL;
 
                 if (controller) {
@@ -953,7 +959,7 @@ int cg_split_spec(const char *spec, char **controller, char **path) {
         t = strndup(spec, e-spec);
         if (!t)
                 return -ENOMEM;
-        if (!filename_is_safe(t)) {
+        if (!cg_controller_is_valid(t, true)) {
                 free(t);
                 return -EINVAL;
         }
@@ -987,18 +993,19 @@ int cg_join_spec(const char *controller, const char *path, char **spec) {
 
         assert(path);
 
+
         if (!controller)
                 controller = "systemd";
-        else if (controller[0] == 0 ||
-                 strchr(controller, ':') ||
-                 strchr(controller, '/'))
-                return -EINVAL;
+        else {
+                if (!cg_controller_is_valid(controller, true))
+                        return -EINVAL;
+
+                controller = normalize_controller(controller);
+        }
 
         if (!path_is_absolute(path))
                 return -EINVAL;
 
-        controller = normalize_controller(controller);
-
         s = strjoin(controller, ":", path, NULL);
         if (!s)
                 return -ENOMEM;
@@ -1008,7 +1015,8 @@ int cg_join_spec(const char *controller, const char *path, char **spec) {
 }
 
 int cg_mangle_path(const char *path, char **result) {
-        char *t, *c, *p;
+        _cleanup_free_ char *c = NULL, *p = NULL;
+        char *t;
         int r;
 
         assert(path);
@@ -1030,11 +1038,7 @@ int cg_mangle_path(const char *path, char **result) {
         if (r < 0)
                 return r;
 
-        r = cg_get_path(c ? c : SYSTEMD_CGROUP_CONTROLLER, p ? p : "/", NULL, result);
-        free(c);
-        free(p);
-
-        return r;
+        return cg_get_path(c ? c : SYSTEMD_CGROUP_CONTROLLER, p ? p : "/", NULL, result);
 }
 
 int cg_get_system_path(char **path) {
@@ -1138,14 +1142,20 @@ char **cg_shorten_controllers(char **controllers) {
 
                 p = normalize_controller(*f);
 
-                if (streq(*f, "systemd")) {
+                if (streq(p, "systemd")) {
+                        free(*f);
+                        continue;
+                }
+
+                if (!cg_controller_is_valid(p, true)) {
+                        log_warning("Controller %s is not valid, removing from controllers list.", p);
                         free(*f);
                         continue;
                 }
 
                 r = check_hierarchy(p);
                 if (r < 0) {
-                        log_debug("Controller %s is not available, removing from controllers list.", *f);
+                        log_debug("Controller %s is not available, removing from controllers list.", p);
                         free(*f);
                         continue;
                 }
@@ -1457,7 +1467,7 @@ int cg_controller_from_attr(const char *attr, char **controller) {
         if (!c)
                 return -ENOMEM;
 
-        if (!filename_is_safe(c)) {
+        if (!cg_controller_is_valid(c, false)) {
                 free(c);
                 return -EINVAL;
         }
@@ -1517,3 +1527,34 @@ char *cg_unescape(const char *p) {
 
         return (char*) p;
 }
+
+#define CONTROLLER_VALID                        \
+        "0123456789"                            \
+        "abcdefghijklmnopqrstuvwxyz"            \
+        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"            \
+        "_"
+
+bool cg_controller_is_valid(const char *p, bool allow_named) {
+        const char *t, *s;
+
+        if (!p)
+                return false;
+
+        if (allow_named) {
+                s = startswith(p, "name=");
+                if (s)
+                        p = s;
+        }
+
+        if (*p == 0 || *p == '_')
+                return false;
+
+        for (t = p; *t; t++)
+                if (!strchr(CONTROLLER_VALID, *t))
+                        return false;
+
+        if (t - p > FILENAME_MAX)
+                return false;
+
+        return true;
+}

src/shared/cgroup-util.h

@@ -96,3 +96,5 @@ int cg_controller_from_attr(const char *attr, char **controller);
 
 char *cg_escape(const char *p);
 char *cg_unescape(const char *p);
+
+bool cg_controller_is_valid(const char *p, bool allow_named);

src/test/test-cgroup-util.c

@@ -153,6 +153,19 @@ static void test_escape(void) {
         test_escape_one("_foobar", "__foobar");
 }
 
+static void test_controller_is_valid(void) {
+        assert_se(cg_controller_is_valid("foobar", false));
+        assert_se(cg_controller_is_valid("foo_bar", false));
+        assert_se(cg_controller_is_valid("name=foo", true));
+        assert_se(!cg_controller_is_valid("", false));
+        assert_se(!cg_controller_is_valid("name=", true));
+        assert_se(!cg_controller_is_valid("=", false));
+        assert_se(!cg_controller_is_valid("cpu,cpuacct", false));
+        assert_se(!cg_controller_is_valid("_", false));
+        assert_se(!cg_controller_is_valid("_foobar", false));
+        assert_se(!cg_controller_is_valid("tatü", false));
+}
+
 int main(void) {
         test_path_decode_unit();
         test_path_get_unit();
@@ -160,6 +173,7 @@ int main(void) {
         test_get_paths();
         test_proc();
         test_escape();
+        test_controller_is_valid();
 
         return 0;
 }