While refactoring cgroup creation, a5bca2152036 ("cgroup: factor out
cgroup_create() out of cgroup_mkdir()") incorrectly onlined subsystems
before the new cgroup is associated with it kernfs_node.  This is fine
for cgroup proper but cgroup_name/path() depend on the associated
kernfs_node and if a subsystem makes the new cgroup_subsys_state
visible, which they're allowed to after onlining, it can lead to NULL
dereference.

The current code performs cgroup creation and subsystem onlining in
cgroup_create() and cgroup_mkdir() makes the cgroup and subsystems
visible afterwards.  There's no reason to online the subsystems early
and we can simply drop cgroup_apply_control_enable() call from
cgroup_create() so that the subsystems are onlined and made visible at
the same time.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Fixes: a5bca2152036 ("cgroup: factor out cgroup_create() out of cgroup_mkdir()") 
Cc: stable@vger.kernel.org # v4.6+

1 files changed, 1 insertions, 1 deletions

diff --git a/trafgen_l2.c b/trafgen_l2.c
index e6c5b59..316d236 100644
--- a/trafgen_l2.c
+++ b/trafgen_l2.c
@@ -31,7 +31,7 @@ static uint16_t pid_to_eth(enum proto_id pid)
 	case PROTO_VLAN:
 		return ETH_P_8021Q;
 	default:
-		panic("eth: Not supported protocol id %u\n", pid);
+		bug();
 	}
 }