Merge branch 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:
 "This contains fixes for two long standing subtle bugs:

   - kthread_bind() on a new kthread binds it to specific CPUs and
     prevents userland from messing with the affinity or cgroup
     membership. Unfortunately, for cgroup membership, there's a window
     between kthread creation and kthread_bind*() invocation where the
     kthread can be moved into a non-root cgroup by userland.

     Depending on what controllers are in effect, this can assign the
     kthread unexpected attributes. For example, in the reported case,
     workqueue workers ended up in a non-root cpuset cgroups and had
     their CPU affinities overridden. This broke workqueue invariants
     and led to workqueue stalls.

     Fixed by closing the window between kthread creation and
     kthread_bind() as suggested by Oleg.

   - There was a bug in cgroup mount path which could allow two
     competing mount attempts to attach the same cgroup_root to two
     different superblocks.

     This was caused by mishandling return value from kernfs_pin_sb().

     Fixed"

* 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: avoid attaching a cgroup root to two different superblocks
  cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 2f26adea0f84..26db528c1d88 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -20,6 +20,7 @@
 #include <linux/freezer.h>
 #include <linux/ptrace.h>
 #include <linux/uaccess.h>
+#include <linux/cgroup.h>
 #include <trace/events/sched.h>
 
 static DEFINE_SPINLOCK(kthread_create_lock);
@@ -225,6 +226,7 @@ static int kthread(void *_create)
 
 	ret = -EINTR;
 	if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
+		cgroup_kthread_ready();
 		__kthread_parkme(self);
 		ret = threadfn(data);
 	}
@@ -538,6 +540,7 @@ int kthreadd(void *unused)
 	set_mems_allowed(node_states[N_MEMORY]);
 
 	current->flags |= PF_NOFREEZE;
+	cgroup_init_kthreadd();
 
 	for (;;) {
 		set_current_state(TASK_INTERRUPTIBLE);