netdev - [PATCH 12/16] drivers, net, ppp: convert asyncppp.refcnt from atomic_t to refcount

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Message-Id: <1490691403-4016-13-git-send-email-elena.reshetova@intel.com>
Date:   Tue, 28 Mar 2017 11:56:39 +0300
From:   Elena Reshetova <elena.reshetova@...el.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rdma@...r.kernel.org, linux-hams@...r.kernel.org,
        linux-ppp@...r.kernel.org, linux-wireless@...r.kernel.org,
        ganeshgr@...lsio.com, nbd@...nwrt.org, blogic@...nwrt.org,
        matthias.bgg@...il.com, yishaih@...lanox.com, saeedm@...lanox.com,
        matanb@...lanox.com, leonro@...lanox.com,
        ajk@...nets.uni-bremen.de, paulus@...ba.org, j@...fi,
        kvalo@...eaurora.org, peterz@...radead.org, keescook@...omium.org,
        gregkh@...uxfoundation.org,
        Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 12/16] drivers, net, ppp: convert asyncppp.refcnt 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>
---
 drivers/net/ppp/ppp_async.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c
index feb9569..2d08f7e 100644
--- a/drivers/net/ppp/ppp_async.c
+++ b/drivers/net/ppp/ppp_async.c
@@ -69,7 +69,7 @@ struct asyncppp {
 
 	struct tasklet_struct tsk;
 
-	atomic_t	refcnt;
+	refcount_t	refcnt;
 	struct semaphore dead_sem;
 	struct ppp_channel chan;	/* interface to generic ppp layer */
 	unsigned char	obuf[OBUFSIZE];
@@ -140,14 +140,14 @@ static struct asyncppp *ap_get(struct tty_struct *tty)
 	read_lock(&disc_data_lock);
 	ap = tty->disc_data;
 	if (ap != NULL)
-		atomic_inc(&ap->refcnt);
+		refcount_inc(&ap->refcnt);
 	read_unlock(&disc_data_lock);
 	return ap;
 }
 
 static void ap_put(struct asyncppp *ap)
 {
-	if (atomic_dec_and_test(&ap->refcnt))
+	if (refcount_dec_and_test(&ap->refcnt))
 		up(&ap->dead_sem);
 }
 
@@ -185,7 +185,7 @@ ppp_asynctty_open(struct tty_struct *tty)
 	skb_queue_head_init(&ap->rqueue);
 	tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);
 
-	atomic_set(&ap->refcnt, 1);
+	refcount_set(&ap->refcnt, 1);
 	sema_init(&ap->dead_sem, 0);
 
 	ap->chan.private = ap;
@@ -234,7 +234,7 @@ ppp_asynctty_close(struct tty_struct *tty)
 	 * our channel ops (i.e. ppp_async_send/ioctl) are in progress
 	 * by the time it returns.
 	 */
-	if (!atomic_dec_and_test(&ap->refcnt))
+	if (!refcount_dec_and_test(&ap->refcnt))
 		down(&ap->dead_sem);
 	tasklet_kill(&ap->tsk);
 
-- 
2.7.4