linux-kernel - [PATCH 17/19] kernel: convert numa_group.refcount from atomic_t to refcount

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Date:   Mon, 20 Feb 2017 12:19:06 +0200
From:   Elena Reshetova <elena.reshetova@...el.com>
To:     linux-kernel@...r.kernel.org
Cc:     cgroups@...r.kernel.org, linux-audit@...hat.com,
        linux-fsdevel@...r.kernel.org, peterz@...radead.org,
        gregkh@...uxfoundation.org, viro@...iv.linux.org.uk, tj@...nel.org,
        mingo@...hat.com, hannes@...xchg.org, lizefan@...wei.com,
        acme@...nel.org, alexander.shishkin@...ux.intel.com,
        paul@...l-moore.com, eparis@...hat.com, akpm@...ux-foundation.org,
        arnd@...db.de, luto@...nel.org,
        Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        Kees Cook <keescook@...omium.org>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 17/19] kernel: convert numa_group.refcount from atomic_t to refcount_t

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.

Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: David Windsor <dwindsor@...il.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 274c747..69405a0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1133,7 +1133,7 @@ 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;
@@ -2181,12 +2181,12 @@ 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);
 }
 
@@ -2207,7 +2207,7 @@ 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