• Tejun Heo's avatar
    cgroup: fix rule checking for threaded mode switching · d1897c95
    Tejun Heo authored
    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+
    d1897c95
cgroup.c 156 KB