netdev - [PATCH 32/36] net, sctp: convert sctp_transport.refcnt from atomic_t to refcount

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Date:   Tue,  4 Jul 2017 15:53:27 +0300
From:   Elena Reshetova <elena.reshetova@...el.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        linux-decnet-user@...ts.sourceforge.net, davem@...emloft.net,
        jmorris@...ei.org, kaber@...sh.net, yoshfuji@...ux-ipv6.org,
        kuznet@....inr.ac.ru, 3chas3@...il.com, ralf@...ux-mips.org,
        stephen@...workplumber.org, jchapman@...alix.com, jhs@...atatu.com,
        bridge@...ts.linux-foundation.org, linux-hams@...r.kernel.org,
        linux-x25@...r.kernel.org, peterz@...radead.org,
        keescook@...omium.org, linux-rdma@...r.kernel.org,
        linux-sctp@...r.kernel.org, vyasevich@...il.com,
        nhorman@...driver.com, linux-nfs@...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,
        Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 32/36] 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 0dfc5c1..6a0d372 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -735,7 +735,7 @@ 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 7cdd6bc..80a97c8 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;
 	}
@@ -311,7 +311,7 @@ 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
@@ -319,7 +319,7 @@ 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