[PATCH 13/15] sched: convert numa_group.refcount from atomic_t to refcount_t

[Elena Reshetova]

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Suggested-by: Kees Cook <keesc...@chromium.org>
Reviewed-by: David Windsor <dwind...@gmail.com>
Reviewed-by: Hans Liljestrand <ishkam...@gmail.com>
Signed-off-by: Elena Reshetova <elena.reshet...@intel.com>
---
 kernel/sched/fair.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c95880e..5f7f997 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1130,7 +1130,7 @@ static void account_numa_dequeue(struct rq *rq, struct 
task_struct *p)
 }
 
 struct numa_group {
-       atomic_t refcount;
+       refcount_t refcount;
 
        spinlock_t lock; /* nr_tasks, tasks */
        int nr_tasks;
@@ -2177,12 +2177,12 @@ static void task_numa_placement(struct task_struct *p)
 
 static inline int get_numa_group(struct numa_group *grp)
 {
-       return atomic_inc_not_zero(&grp->refcount);
+       return refcount_inc_not_zero(&grp->refcount);
 }
 
 static inline void put_numa_group(struct numa_group *grp)
 {
-       if (atomic_dec_and_test(&grp->refcount))
+       if (refcount_dec_and_test(&grp->refcount))
                kfree_rcu(grp, rcu);
 }
 
@@ -2203,7 +2203,7 @@ static void task_numa_group(struct task_struct *p, int 
cpupid, int flags,
                if (!grp)
                        return;
 
-               atomic_set(&grp->refcount, 1);
+               refcount_set(&grp->refcount, 1);
                grp->active_nodes = 1;
                grp->max_faults_cpu = 0;
                spin_lock_init(&grp->lock);
-- 
2.7.4