net: convert nf_bridge_info.use 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@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a17e235..005793e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -252,7 +252,7 @@ struct nf_conntrack {
 
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 struct nf_bridge_info {
-	atomic_t		use;
+	refcount_t		use;
 	enum {
 		BRNF_PROTO_UNCHANGED,
 		BRNF_PROTO_8021Q,
@@ -3589,13 +3589,13 @@ static inline void nf_conntrack_get(struct nf_conntrack *nfct)
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
 {
-	if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
+	if (nf_bridge && refcount_dec_and_test(&nf_bridge->use))
 		kfree(nf_bridge);
 }
 static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
 {
 	if (nf_bridge)
-		atomic_inc(&nf_bridge->use);
+		refcount_inc(&nf_bridge->use);
 }
 #endif /* CONFIG_BRIDGE_NETFILTER */
 static inline void nf_reset(struct sk_buff *skb)