Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d1897c95 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: fix rule checking for threaded mode switching 



A domain cgroup isn't allowed to be turned threaded if its subtree is
populated or domain controllers are enabled.  cgroup_enable_threaded()
depended on cgroup_can_be_thread_root() test to enforce this rule.  A
parent which has populated domain descendants or have domain
controllers enabled can't become a thread root, so the above rules are
enforced automatically.

However, for the root cgroup which can host mixed domain and threaded
children, cgroup_can_be_thread_root() doesn't check any of those
conditions and thus first level cgroups ends up escaping those rules.

This patch fixes the bug by adding explicit checks for those rules in
cgroup_enable_threaded().

Reported-by: default avatarMichael Kerrisk (man-pages) <mtk.manpages@gmail.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Fixes: 8cfd8147 ("cgroup: implement cgroup v2 thread support")
Cc: stable@vger.kernel.org # v4.14+
parent c53593e5

kernel/cgroup/cgroup.c

+10 −0
Original line number Diff line number Diff line
@@ -3183,6 +3183,16 @@ static int cgroup_enable_threaded(struct cgroup *cgrp) 
	if (cgroup_is_threaded(cgrp))

		return 0;



	/*

	 * If @cgroup is populated or has domain controllers enabled, it

	 * can't be switched.  While the below cgroup_can_be_thread_root()

	 * test can catch the same conditions, that's only when @parent is

	 * not mixable, so let's check it explicitly.

	 */

	if (cgroup_is_populated(cgrp) ||

	    cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)

		return -EOPNOTSUPP;



	/* we're joining the parent's domain, ensure its validity */

	if (!cgroup_is_valid_domain(dom_cgrp) ||

	    !cgroup_can_be_thread_root(dom_cgrp))