cpuset: make sure new tasks conform to the current config of the cpuset

A new task inherits cpus_allowed and mems_allowed masks from its parent,
but if someone changes cpuset's config by writing to cpuset.cpus/cpuset.mems
before this new task is inserted into the cgroup's task list, the new task
won't be updated accordingly.

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

1 files changed, 15 insertions, 0 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c7fd2778ed50..c27e53326bef 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2069,6 +2069,20 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
         mutex_unlock(&cpuset_mutex);
 }
 
+/*
+ * Make sure the new task conform to the current state of its parent,
+ * which could have been changed by cpuset just after it inherits the
+ * state from the parent and before it sits on the cgroup's task list.
+ */
+void cpuset_fork(struct task_struct *task)
+{
+        if (task_css_is_root(task, cpuset_cgrp_id))
+                return;
+
+        set_cpus_allowed_ptr(task, &current->cpus_allowed);
+        task->mems_allowed = current->mems_allowed;
+}
+
 struct cgroup_subsys cpuset_cgrp_subsys = {
         .css_alloc      = cpuset_css_alloc,
         .css_online     = cpuset_css_online,
@@ -2079,6 +2093,7 @@ struct cgroup_subsys cpuset_cgrp_subsys = {
         .attach         = cpuset_attach,
         .post_attach    = cpuset_post_attach,
         .bind           = cpuset_bind,
+        .fork           = cpuset_fork,
         .legacy_cftypes = files,
         .early_init     = true,
 };