netdev - [PATCH 19/23] net, sctp: convert sctp_transport.refcnt from atomic_t to refcount

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Message-Id: <1489752646-8749-20-git-send-email-elena.reshetova@intel.com>
Date:   Fri, 17 Mar 2017 14:10:42 +0200
From:   Elena Reshetova <elena.reshetova@...el.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        davem@...emloft.net, linux-x25@...r.kernel.org,
        linux-sctp@...r.kernel.org, vyasevich@...il.com,
        nhorman@...driver.com, linux-hams@...r.kernel.org,
        linux-nfs@...r.kernel.org, ceph-devel@...r.kernel.org,
        zyan@...hat.com, sage@...hat.com, bfields@...ldses.org,
        jlayton@...chiereds.net, steffen.klassert@...unet.com,
        herbert@...dor.apana.org.au, santosh.shilimkar@...cle.com,
        jreuter@...na.de, ralf@...ux-mips.org, peterz@...radead.org,
        keescook@...omium.org, Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 19/23] net, sctp: convert sctp_transport.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>
---
 include/net/sctp/structs.h | 2 +-
 net/sctp/transport.c       | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index 7ee0c26..ac3184e 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -731,7 +731,7 @@ struct sctp_transport {
 	struct rhlist_head node;
 
 	/* Reference counting. */
-	atomic_t refcnt;
+	refcount_t refcnt;
 		/* RTO-Pending : A flag used to track if one of the DATA
 		 *		chunks sent to this address is currently being
 		 *		used to compute a RTT. If this flag is 0,
diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 3379668..45a5774 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -99,7 +99,7 @@ static struct sctp_transport *sctp_transport_init(struct net *net,
 	/* Initialize the 64-bit random nonce sent with heartbeat. */
 	get_random_bytes(&peer->hb_nonce, sizeof(peer->hb_nonce));
 
-	atomic_set(&peer->refcnt, 1);
+	refcount_set(&peer->refcnt, 1);
 
 	return peer;
 }
@@ -172,7 +172,7 @@ static void sctp_transport_destroy_rcu(struct rcu_head *head)
  */
 static void sctp_transport_destroy(struct sctp_transport *transport)
 {
-	if (unlikely(atomic_read(&transport->refcnt))) {
+	if (unlikely(refcount_read(&transport->refcnt))) {
 		WARN(1, "Attempt to destroy undead transport %p!\n", transport);
 		return;
 	}
@@ -316,7 +316,7 @@ void sctp_transport_route(struct sctp_transport *transport,
 /* Hold a reference to a transport.  */
 int sctp_transport_hold(struct sctp_transport *transport)
 {
-	return atomic_add_unless(&transport->refcnt, 1, 0);
+	return refcount_inc_not_zero(&transport->refcnt);
 }
 
 /* Release a reference to a transport and clean up
@@ -324,7 +324,7 @@ int sctp_transport_hold(struct sctp_transport *transport)
  */
 void sctp_transport_put(struct sctp_transport *transport)
 {
-	if (atomic_dec_and_test(&transport->refcnt))
+	if (refcount_dec_and_test(&transport->refcnt))
 		sctp_transport_destroy(transport);
 }
 
-- 
2.7.4