netdev - [PATCH 34/36] net, ax25: convert ax25_uid_assoc.refcount from atomic_t to refcount

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Date:   Tue,  4 Jul 2017 15:53:29 +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 34/36] net, ax25: convert ax25_uid_assoc.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  | 8 ++++----
 net/ax25/ax25_uid.c | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/ax25.h b/include/net/ax25.h
index e602f81..edd82f0 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -11,7 +11,7 @@
 #include <linux/timer.h>
 #include <linux/list.h>
 #include <linux/slab.h>
-#include <linux/atomic.h>
+#include <linux/refcount.h>
 #include <net/neighbour.h>
 #include <net/sock.h>
 
@@ -158,7 +158,7 @@ enum {
 
 typedef struct ax25_uid_assoc {
 	struct hlist_node	uid_node;
-	atomic_t		refcount;
+	refcount_t		refcount;
 	kuid_t			uid;
 	ax25_address		call;
 } ax25_uid_assoc;
@@ -167,11 +167,11 @@ typedef struct ax25_uid_assoc {
 	hlist_for_each_entry(__ax25, list, uid_node)
 
 #define ax25_uid_hold(ax25) \
-	atomic_inc(&((ax25)->refcount))
+	refcount_inc(&((ax25)->refcount))
 
 static inline void ax25_uid_put(ax25_uid_assoc *assoc)
 {
-	if (atomic_dec_and_test(&assoc->refcount)) {
+	if (refcount_dec_and_test(&assoc->refcount)) {
 		kfree(assoc);
 	}
 }
diff --git a/net/ax25/ax25_uid.c b/net/ax25/ax25_uid.c
index 0403b0d..83b035f 100644
--- a/net/ax25/ax25_uid.c
+++ b/net/ax25/ax25_uid.c
@@ -107,7 +107,7 @@ int ax25_uid_ioctl(int cmd, struct sockaddr_ax25 *sax)
 		if ((ax25_uid = kmalloc(sizeof(*ax25_uid), GFP_KERNEL)) == NULL)
 			return -ENOMEM;
 
-		atomic_set(&ax25_uid->refcount, 1);
+		refcount_set(&ax25_uid->refcount, 1);
 		ax25_uid->uid  = sax25_kuid;
 		ax25_uid->call = sax->sax25_call;
 
-- 
2.7.4