linux-kernel - [PATCH 36/36] net, ax25: convert ax25_cb.refcount from atomic_t to refcount

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Message-Id: <1499172811-16271-37-git-send-email-elena.reshetova@intel.com>
Date:   Tue,  4 Jul 2017 15:53:31 +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 36/36] net, ax25: convert ax25_cb.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>
---
 include/net/ax25.h | 6 +++---
 net/ax25/af_ax25.c | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/net/ax25.h b/include/net/ax25.h
index e3467ba..c4a0cf6 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -244,7 +244,7 @@ typedef struct ax25_cb {
 	unsigned char		window;
 	struct timer_list	timer, dtimer;
 	struct sock		*sk;		/* Backlink to socket */
-	atomic_t		refcount;
+	refcount_t		refcount;
 } ax25_cb;
 
 struct ax25_sock {
@@ -266,11 +266,11 @@ static inline struct ax25_cb *sk_to_ax25(const struct sock *sk)
 	hlist_for_each_entry(__ax25, list, ax25_node)
 
 #define ax25_cb_hold(__ax25) \
-	atomic_inc(&((__ax25)->refcount))
+	refcount_inc(&((__ax25)->refcount))
 
 static __inline__ void ax25_cb_put(ax25_cb *ax25)
 {
-	if (atomic_dec_and_test(&ax25->refcount)) {
+	if (refcount_dec_and_test(&ax25->refcount)) {
 		kfree(ax25->digipeat);
 		kfree(ax25);
 	}
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 0c92ba0..f3f9d18 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -510,7 +510,7 @@ ax25_cb *ax25_create_cb(void)
 	if ((ax25 = kzalloc(sizeof(*ax25), GFP_ATOMIC)) == NULL)
 		return NULL;
 
-	atomic_set(&ax25->refcount, 1);
+	refcount_set(&ax25->refcount, 1);
 
 	skb_queue_head_init(&ax25->write_queue);
 	skb_queue_head_init(&ax25->frag_queue);
-- 
2.7.4