Michal Koutný 3ea87219a9 cgroup: Prevent double killing of css when enabling threaded cgroup ... commit 3bc0bb36fa upstream. The test_cgcore_no_internal_process_constraint_on_threads selftest when running with subsystem controlling noise triggers two warnings: > [ 597.443115] WARNING: CPU: 1 PID: 28167 at kernel/cgroup/cgroup.c:3131 cgroup_apply_control_enable+0xe0/0x3f0 > [ 597.443413] WARNING: CPU: 1 PID: 28167 at kernel/cgroup/cgroup.c:3177 cgroup_apply_control_disable+0xa6/0x160 Both stem from a call to cgroup_type_write. The first warning was also triggered by syzkaller. When we're switching cgroup to threaded mode shortly after a subsystem was disabled on it, we can see the respective subsystem css dying there. The warning in cgroup_apply_control_enable is harmless in this case since we're not adding new subsys anyway. The warning in cgroup_apply_control_disable indicates an attempt to kill css of recently disabled subsystem repeatedly. The commit prevents these situations by making cgroup_type_write wait for all dying csses to go away before re-applying subtree controls. When at it, the locations of WARN_ON_ONCE calls are moved so that warning is triggered only when we are about to misuse the dying css. Reported-by: syzbot+5493b2a54d31d6aea629@syzkaller.appspotmail.com Reported-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Michal Koutný <mkoutny@suse.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-02-05 21:22:42 +00:00
..
Makefile	cgroup: cgroup v2 freezer	2019-04-19 11:26:48 -07:00
cgroup-internal.h	cgroup: make TRACE_CGROUP_PATH irq-safe	2019-04-19 11:26:49 -07:00
cgroup-v1.c	Use kvmalloc in cgroups-v1	2019-08-07 11:37:58 -07:00
cgroup.c	cgroup: Prevent double killing of css when enabling threaded cgroup	2020-02-05 21:22:42 +00:00
cpuset.c	sched/topology: Don't try to build empty sched domains	2019-10-29 09:58:45 +01:00
debug.c	kernel: cgroup: fix misuse of %x	2019-05-06 08:47:48 -07:00
freezer.c	cgroup: freezer: don't change task and cgroups status unnecessarily	2019-12-31 16:45:06 +01:00
legacy_freezer.c	cgroup: rename freezer.c into legacy_freezer.c	2019-04-19 11:26:48 -07:00
namespace.c	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
pids.c	cgroup: pids: use atomic64_t for pids->limit	2019-12-17 19:56:15 +01:00
rdma.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 451	2019-06-19 17:09:08 +02:00
rstat.c	treewide: Add SPDX license identifier for missed files	2019-05-21 10:50:45 +02:00