netdev - [PATCH 17/18] net, netrom: convert nr_neigh.refcount from atomic_t to refcount

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Date:   Fri, 17 Mar 2017 13:12:58 +0200
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, linux-bluetooth@...r.kernel.org,
        marcel@...tmann.org, johan.hedberg@...il.com, peterz@...radead.org,
        keescook@...omium.org, Elena Reshetova <elena.reshetova@...el.com>,
        Hans Liljestrand <ishkamiel@...il.com>,
        David Windsor <dwindsor@...il.com>
Subject: [PATCH 17/18] net, netrom: convert nr_neigh.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/netrom.h  | 7 ++++---
 net/netrom/nr_route.c | 4 ++--
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/net/netrom.h b/include/net/netrom.h
index 110350a..cecb4fd 100644
--- a/include/net/netrom.h
+++ b/include/net/netrom.h
@@ -11,6 +11,7 @@
 #include <linux/list.h>
 #include <linux/slab.h>
 #include <net/sock.h>
+#include <linux/refcount.h>
 
 #define	NR_NETWORK_LEN			15
 #define	NR_TRANSPORT_LEN		5
@@ -93,7 +94,7 @@ struct nr_neigh {
 	unsigned short		count;
 	unsigned int		number;
 	unsigned char		failed;
-	atomic_t		refcount;
+	refcount_t		refcount;
 };
 
 struct nr_route {
@@ -128,11 +129,11 @@ static __inline__ void nr_node_put(struct nr_node *nr_node)
 }
 
 #define nr_neigh_hold(__nr_neigh) \
-	atomic_inc(&((__nr_neigh)->refcount))
+	refcount_inc(&((__nr_neigh)->refcount))
 
 static __inline__ void nr_neigh_put(struct nr_neigh *nr_neigh)
 {
-	if (atomic_dec_and_test(&nr_neigh->refcount)) {
+	if (refcount_dec_and_test(&nr_neigh->refcount)) {
 		if (nr_neigh->ax25)
 			ax25_cb_put(nr_neigh->ax25);
 		kfree(nr_neigh->digipeat);
diff --git a/net/netrom/nr_route.c b/net/netrom/nr_route.c
index d72a4f1..6b72970 100644
--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -149,7 +149,7 @@ static int __must_check nr_add_node(ax25_address *nr, const char *mnemonic,
 		nr_neigh->count    = 0;
 		nr_neigh->number   = nr_neigh_no++;
 		nr_neigh->failed   = 0;
-		atomic_set(&nr_neigh->refcount, 1);
+		refcount_set(&nr_neigh->refcount, 1);
 
 		if (ax25_digi != NULL && ax25_digi->ndigi > 0) {
 			nr_neigh->digipeat = kmemdup(ax25_digi,
@@ -431,7 +431,7 @@ static int __must_check nr_add_neigh(ax25_address *callsign,
 	nr_neigh->count    = 0;
 	nr_neigh->number   = nr_neigh_no++;
 	nr_neigh->failed   = 0;
-	atomic_set(&nr_neigh->refcount, 1);
+	refcount_set(&nr_neigh->refcount, 1);
 
 	if (ax25_digi != NULL && ax25_digi->ndigi > 0) {
 		nr_neigh->digipeat = kmemdup(ax25_digi, sizeof(*ax25_digi),
-- 
2.7.4