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| author | Tejun Heo <tj@kernel.org> | 2018-02-21 20:39:22 +0100 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2018-02-21 20:39:22 +0100 |
| commit | d1897c9538edafd4ae6bbd03cc075962ddde2c21 (patch) | |
| tree | 96b73265ed9e288fdcd2d153c3e045ef83ec916e | |
| parent | sched, cgroup: Don't reject lower cpu.max on ancestors (diff) | |
| download | linux-d1897c9538edafd4ae6bbd03cc075962ddde2c21.tar.xz linux-d1897c9538edafd4ae6bbd03cc075962ddde2c21.zip | |
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: Michael Kerrisk (man-pages) <mtk.manpages@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: 8cfd8147df67 ("cgroup: implement cgroup v2 thread support")
Cc: stable@vger.kernel.org # v4.14+
| -rw-r--r-- | kernel/cgroup/cgroup.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 8cda3bc3ae22..4bfb2908ec15 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -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)) |