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-rw-r--r--kernel/cgroup/cgroup.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 19784d44d615..9bb255e41cf2 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6285,7 +6285,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
if (!buf)
goto out;
- cgroup_lock();
+ rcu_read_lock();
spin_lock_irq(&css_set_lock);
for_each_root(root) {
@@ -6296,6 +6296,11 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
if (root == &cgrp_dfl_root && !READ_ONCE(cgrp_dfl_visible))
continue;
+ cgrp = task_cgroup_from_root(tsk, root);
+ /* The root has already been unmounted. */
+ if (!cgrp)
+ continue;
+
seq_printf(m, "%d:", root->hierarchy_id);
if (root != &cgrp_dfl_root)
for_each_subsys(ss, ssid)
@@ -6306,9 +6311,6 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
seq_printf(m, "%sname=%s", count ? "," : "",
root->name);
seq_putc(m, ':');
-
- cgrp = task_cgroup_from_root(tsk, root);
-
/*
* On traditional hierarchies, all zombie tasks show up as
* belonging to the root cgroup. On the default hierarchy,
@@ -6340,7 +6342,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
retval = 0;
out_unlock:
spin_unlock_irq(&css_set_lock);
- cgroup_unlock();
+ rcu_read_unlock();
kfree(buf);
out:
return retval;