linux-kernel - [PATCH 16/23] net, sctp: convert sctp_auth_bytes.refcnt from atomic_t to refcount

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Date:   Fri, 17 Mar 2017 14:10:39 +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 16/23] net, sctp: convert sctp_auth_bytes.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/auth.h | 5 +++--
 net/sctp/auth.c         | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/net/sctp/auth.h b/include/net/sctp/auth.h
index 9b9fb12..328fccc 100644
--- a/include/net/sctp/auth.h
+++ b/include/net/sctp/auth.h
@@ -31,6 +31,7 @@
 #define __sctp_auth_h__
 
 #include <linux/list.h>
+#include <linux/refcount.h>
 
 struct sctp_endpoint;
 struct sctp_association;
@@ -53,7 +54,7 @@ struct sctp_hmac {
  * over SCTP-AUTH
  */
 struct sctp_auth_bytes {
-	atomic_t refcnt;
+	refcount_t refcnt;
 	__u32 len;
 	__u8  data[];
 };
@@ -76,7 +77,7 @@ static inline void sctp_auth_key_hold(struct sctp_auth_bytes *key)
 	if (!key)
 		return;
 
-	atomic_inc(&key->refcnt);
+	refcount_inc(&key->refcnt);
 }
 
 void sctp_auth_key_put(struct sctp_auth_bytes *key);
diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index f99d485..b6c98fe 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -63,7 +63,7 @@ void sctp_auth_key_put(struct sctp_auth_bytes *key)
 	if (!key)
 		return;
 
-	if (atomic_dec_and_test(&key->refcnt)) {
+	if (refcount_dec_and_test(&key->refcnt)) {
 		kzfree(key);
 		SCTP_DBG_OBJCNT_DEC(keys);
 	}
@@ -84,7 +84,7 @@ static struct sctp_auth_bytes *sctp_auth_create_key(__u32 key_len, gfp_t gfp)
 		return NULL;
 
 	key->len = key_len;
-	atomic_set(&key->refcnt, 1);
+	refcount_set(&key->refcnt, 1);
 	SCTP_DBG_OBJCNT_INC(keys);
 
 	return key;
-- 
2.7.4