[PATCH] cgroup: missing rcu read lock around task_css_set

[Sasha Levin]

rcu read lock should be held when calling and working with task_css_set.

This patch also fixes a related lockdep warning.

Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
 kernel/cgroup.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 8f4ddbe..f638ad6 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4361,6 +4361,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
 	}
 
 	/* Reassign the task to the init_css_set. */
+	rcu_read_lock();
 	cset = task_css_set(tsk);
 	RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
 
@@ -4378,6 +4379,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
 
 	if (put_cset)
 		put_css_set(cset, true);
+	rcu_read_unlock();
 }
 
 static void check_for_release(struct cgroup *cgrp)
-- 
1.7.2.5

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