Michal Koutný 6d26630912 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 14:43:39 +00:00
..
cgroup-internal.h	cgroup/tracing: Move taking of spin lock out of trace event handlers	2018-07-11 10:48:47 -07:00
cgroup-v1.c	cgroup/tracing: Move taking of spin lock out of trace event handlers	2018-07-11 10:48:47 -07:00
cgroup.c	cgroup: Prevent double killing of css when enabling threaded cgroup	2020-02-05 14:43:39 +00:00
cpuset.c	cpuset: restore sanity to cpuset_cpus_allowed_fallback()	2019-07-10 09:53:39 +02:00
debug.c	debug cgroup: use task_css_set instead of rcu_dereference	2017-11-27 11:37:33 -08:00
freezer.c
Makefile	cgroup: Rename kernel/cgroup/stat.c to kernel/cgroup/rstat.c	2018-04-26 14:29:04 -07:00
namespace.c
pids.c	cgroup: pids: use atomic64_t for pids->limit	2019-12-17 20:34:56 +01:00
rdma.c	rdmacg: Convert to use match_string() helper	2018-05-07 09:27:26 -07:00
rstat.c	cgroup, rstat: Don't flush subtree root unless necessary	2019-04-05 22:33:06 +02:00