[PATCH 9/8] cgroup: fix RCU related sparse warnings

[Tejun Heo]

>From 9ca76e7e3cb885bc5701e9b1fe90c44f4aef123a Mon Sep 17 00:00:00 2001
From: Tejun Heo <t...@kernel.org>
Date: Thu, 22 Dec 2016 12:28:01 -0500

kn->priv which is a void * is used as a RCU pointer by cgroup.  When
dereferencing it, it was passing kn->priv to rcu_derefreence() without
casting it into a RCU pointer triggering address space mismatch
warning from sparse.  Fix them.

Signed-off-by: Tejun Heo <t...@kernel.org>
Reported-by: Fengguang Wu <fengguang...@intel.com>
---
 kernel/cgroup/cgroup-v1.c | 2 +-
 kernel/cgroup/cgroup.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 37be09e..465b101 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -694,7 +694,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct 
dentry *dentry)
         * @kn->priv is RCU safe.  Let's do the RCU dancing.
         */
        rcu_read_lock();
-       cgrp = rcu_dereference(kn->priv);
+       cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
        if (!cgrp || cgroup_is_dead(cgrp)) {
                rcu_read_unlock();
                mutex_unlock(&cgroup_mutex);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index b6b9068..d9d82e9 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4932,7 +4932,7 @@ struct cgroup_subsys_state 
*css_tryget_online_from_dir(struct dentry *dentry,
         * have been or be removed at any point.  @kn->priv is RCU
         * protected for this access.  See css_release_work_fn() for details.
         */
-       cgrp = rcu_dereference(kn->priv);
+       cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
        if (cgrp)
                css = cgroup_css(cgrp, ss);
 
-- 
2.9.3