Commit 97a61369 authored Sep 12, 2019 by Roman Gushchin Committed by Tejun Heo Sep 12, 2019

cgroup: freezer: fix frozen state inheritance



If a new child cgroup is created in the frozen cgroup hierarchy
(one or more of ancestor cgroups is frozen), the CGRP_FREEZE cgroup
flag should be set. Otherwise if a process will be attached to the
child cgroup, it won't become frozen.

The problem can be reproduced with the test_cgfreezer_mkdir test.

This is the output before this patch:
  ~/test_freezer
  ok 1 test_cgfreezer_simple
  ok 2 test_cgfreezer_tree
  ok 3 test_cgfreezer_forkbomb
  Cgroup /sys/fs/cgroup/cg_test_mkdir_A/cg_test_mkdir_B isn't frozen
  not ok 4 test_cgfreezer_mkdir
  ok 5 test_cgfreezer_rmdir
  ok 6 test_cgfreezer_migrate
  ok 7 test_cgfreezer_ptrace
  ok 8 test_cgfreezer_stopped
  ok 9 test_cgfreezer_ptraced
  ok 10 test_cgfreezer_vfork

And with this patch:
  ~/test_freezer
  ok 1 test_cgfreezer_simple
  ok 2 test_cgfreezer_tree
  ok 3 test_cgfreezer_forkbomb
  ok 4 test_cgfreezer_mkdir
  ok 5 test_cgfreezer_rmdir
  ok 6 test_cgfreezer_migrate
  ok 7 test_cgfreezer_ptrace
  ok 8 test_cgfreezer_stopped
  ok 9 test_cgfreezer_ptraced
  ok 10 test_cgfreezer_vfork

Reported-by: Mark Crossen <mcrossen@fb.com>
Signed-off-by: Roman Gushchin <guro@fb.com>
Fixes: 76f969e8 ("cgroup: cgroup v2 freezer")
Cc: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Tejun Heo <tj@kernel.org>

parent 44e9d308

kernel/cgroup/cgroup.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -5255,8 +5255,16 @@ static struct cgroup cgroup_create(struct cgroup parent)
		* if the parent has to be frozen, the child has too.
		*/
		cgrp->freezer.e_freeze = parent->freezer.e_freeze;
		if (cgrp->freezer.e_freeze)
		if (cgrp->freezer.e_freeze) {
		/*
		* Set the CGRP_FREEZE flag, so when a process will be
		* attached to the child cgroup, it will become frozen.
		* At this point the new cgroup is unpopulated, so we can
		* consider it frozen immediately.
		*/
		set_bit(CGRP_FREEZE, &cgrp->flags);
		set_bit(CGRP_FROZEN, &cgrp->flags);
		}

		spin_lock_irq(&css_set_lock);
		for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {

Admin message