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authorTejun Heo <tj@kernel.org>2018-02-21 11:39:22 -0800
committerTejun Heo <tj@kernel.org>2018-02-21 11:39:22 -0800
commitd1897c9538edafd4ae6bbd03cc075962ddde2c21 (patch)
tree96b73265ed9e288fdcd2d153c3e045ef83ec916e /kernel
parentc53593e5cb693d59d9e8b64fb3a79436bf99c3b3 (diff)
downloadlinux-d1897c9538edafd4ae6bbd03cc075962ddde2c21.tar.bz2
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+
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup/cgroup.c10
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))