cpuset: fix a regression in validating config change

It's not allowed to clear masks of a cpuset if there're tasks in it,
but it's broken:

  # mkdir /cgroup/sub
  # echo 0 > /cgroup/sub/cpuset.cpus
  # echo 0 > /cgroup/sub/cpuset.mems
  # echo $$ > /cgroup/sub/tasks
  # echo > /cgroup/sub/cpuset.cpus
  (should fail)

This bug was introduced by commit 88fa523bff295f1d60244a54833480b02f775152
("cpuset: allow to move tasks to empty cpusets").

tj: Dropped temp bool variables and nestes the conditionals directly.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 9 insertions, 5 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 010a0083c0ae..ea1966db34f2 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -475,13 +475,17 @@ static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
 
         /*
          * Cpusets with tasks - existing or newly being attached - can't
-         * have empty cpus_allowed or mems_allowed.
+         * be changed to have empty cpus_allowed or mems_allowed.
          */
         ret = -ENOSPC;
-        if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress) &&
-            (cpumask_empty(trial->cpus_allowed) &&
-             nodes_empty(trial->mems_allowed)))
-                goto out;
+        if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress)) {
+                if (!cpumask_empty(cur->cpus_allowed) &&
+                    cpumask_empty(trial->cpus_allowed))
+                        goto out;
+                if (!nodes_empty(cur->mems_allowed) &&
+                    nodes_empty(trial->mems_allowed))
+                        goto out;
+        }
 
         ret = 0;
 out: