batman-adv: Check return value of try_module_get

New operations should not be started when they need an increased module
reference counter and try_module_get failed.

This patch addresses Coverity #712284: Unchecked return value
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>

net/batman-adv/debugfs.c

@@ -99,15 +99,17 @@ int batadv_debug_log(struct batadv_priv *bat_priv, const char *fmt, ...)
 
 static int batadv_log_open(struct inode *inode, struct file *file)
 {
+	if (!try_module_get(THIS_MODULE))
+		return -EBUSY;
+
 	nonseekable_open(inode, file);
 	file->private_data = inode->i_private;
-	batadv_inc_module_count();
 	return 0;
 }
 
 static int batadv_log_release(struct inode *inode, struct file *file)
 {
-	batadv_dec_module_count();
+	module_put(THIS_MODULE);
 	return 0;
 }
 

net/batman-adv/icmp_socket.c

@@ -42,12 +42,16 @@ static int batadv_socket_open(struct inode *inode, struct file *file)
 	unsigned int i;
 	struct batadv_socket_client *socket_client;
 
+	if (!try_module_get(THIS_MODULE))
+		return -EBUSY;
+
 	nonseekable_open(inode, file);
 
 	socket_client = kmalloc(sizeof(*socket_client), GFP_KERNEL);
-
-	if (!socket_client)
+	if (!socket_client) {
+		module_put(THIS_MODULE);
 		return -ENOMEM;
+	}
 
 	for (i = 0; i < ARRAY_SIZE(batadv_socket_client_hash); i++) {
 		if (!batadv_socket_client_hash[i]) {
@@ -59,6 +63,7 @@ static int batadv_socket_open(struct inode *inode, struct file *file)
 	if (i == ARRAY_SIZE(batadv_socket_client_hash)) {
 		pr_err("Error - can't add another packet client: maximum number of clients reached\n");
 		kfree(socket_client);
+		module_put(THIS_MODULE);
 		return -EXFULL;
 	}
 
@@ -71,7 +76,6 @@ static int batadv_socket_open(struct inode *inode, struct file *file)
 
 	file->private_data = socket_client;
 
-	batadv_inc_module_count();
 	return 0;
 }
 
@@ -96,7 +100,7 @@ static int batadv_socket_release(struct inode *inode, struct file *file)
 	spin_unlock_bh(&socket_client->lock);
 
 	kfree(socket_client);
-	batadv_dec_module_count();
+	module_put(THIS_MODULE);
 
 	return 0;
 }

net/batman-adv/main.c

@@ -160,16 +160,6 @@ void batadv_mesh_free(struct net_device *soft_iface)
 	atomic_set(&bat_priv->mesh_state, BATADV_MESH_INACTIVE);
 }
 
-void batadv_inc_module_count(void)
-{
-	try_module_get(THIS_MODULE);
-}
-
-void batadv_dec_module_count(void)
-{
-	module_put(THIS_MODULE);
-}
-
 int batadv_is_my_mac(const uint8_t *addr)
 {
 	const struct batadv_hard_iface *hard_iface;

net/batman-adv/main.h

@@ -150,8 +150,6 @@ extern struct workqueue_struct *batadv_event_workqueue;
 
 int batadv_mesh_init(struct net_device *soft_iface);
 void batadv_mesh_free(struct net_device *soft_iface);
-void batadv_inc_module_count(void);
-void batadv_dec_module_count(void);
 int batadv_is_my_mac(const uint8_t *addr);
 struct batadv_hard_iface *
 batadv_seq_print_text_primary_if_get(struct seq_file *seq);