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authorMike Galbraith <mgalbraith@suse.de>2012-04-21 09:13:46 +0200
committerTejun Heo <tj@kernel.org>2012-04-23 11:03:51 -0700
commitc4c27fbdda4e8ba87806c415b6d15266b07bce4b (patch)
treee532518e0942a2562642744103eb64554c8abbda /kernel/cgroup.c
parent86f82d561864e902c70282b6f17cf590c0f34691 (diff)
cgroups: disallow attaching kthreadd or PF_THREAD_BOUND threads
Allowing kthreadd to be moved to a non-root group makes no sense, it being a global resource, and needlessly leads unsuspecting users toward trouble. 1. An RT workqueue worker thread spawned in a task group with no rt_runtime allocated is not schedulable. Simple user error, but harmful to the box. 2. A worker thread which acquires PF_THREAD_BOUND can never leave a cpuset, rendering the cpuset immortal. Save the user some unexpected trouble, just say no. Signed-off-by: Mike Galbraith <mgalbraith@suse.de> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b2f203f25ec..ad8eae5bb80 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -60,6 +60,7 @@
#include <linux/eventfd.h>
#include <linux/poll.h>
#include <linux/flex_array.h> /* used in cgroup_attach_proc */
+#include <linux/kthread.h>
#include <linux/atomic.h>
@@ -2225,6 +2226,18 @@ retry_find_task:
if (threadgroup)
tsk = tsk->group_leader;
+
+ /*
+ * Workqueue threads may acquire PF_THREAD_BOUND and become
+ * trapped in a cpuset, or RT worker may be born in a cgroup
+ * with no rt_runtime allocated. Just say no.
+ */
+ if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
+ ret = -EINVAL;
+ rcu_read_unlock();
+ goto out_unlock_cgroup;
+ }
+
get_task_struct(tsk);
rcu_read_unlock();