net: rose: fix netdev reference changes

Bernard reported that trying to unload rose module would lead
to infamous messages:

unregistered_netdevice: waiting for rose0 to become free. Usage count = xx

This patch solves the issue, by making sure each socket referring to
a netdevice holds a reference count on it, and properly releases it
in rose_release().

rose_dev_first() is also fixed to take a device reference
before leaving the rcu_read_locked section.

Following patch will add ref_tracker annotations to ease
future bug hunting.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Reported-by: Bernard Pidoux <f6bvp@free.fr>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Bernard Pidoux <f6bvp@free.fr>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/rose/af_rose.c

@@ -192,6 +192,7 @@ static void rose_kill_by_device(struct net_device *dev)
 			rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0);
 			if (rose->neighbour)
 				rose->neighbour->use--;
+			dev_put(rose->device);
 			rose->device = NULL;
 		}
 	}
@@ -592,6 +593,8 @@ static struct sock *rose_make_new(struct sock *osk)
 	rose->idle	= orose->idle;
 	rose->defer	= orose->defer;
 	rose->device	= orose->device;
+	if (rose->device)
+		dev_hold(rose->device);
 	rose->qbitincl	= orose->qbitincl;
 
 	return sk;
@@ -645,6 +648,7 @@ static int rose_release(struct socket *sock)
 		break;
 	}
 
+	dev_put(rose->device);
 	sock->sk = NULL;
 	release_sock(sk);
 	sock_put(sk);
@@ -721,7 +725,6 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
 	struct rose_sock *rose = rose_sk(sk);
 	struct sockaddr_rose *addr = (struct sockaddr_rose *)uaddr;
 	unsigned char cause, diagnostic;
-	struct net_device *dev;
 	ax25_uid_assoc *user;
 	int n, err = 0;
 
@@ -778,9 +781,12 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
 	}
 
 	if (sock_flag(sk, SOCK_ZAPPED)) {	/* Must bind first - autobinding in this may or may not work */
+		struct net_device *dev;
+
 		sock_reset_flag(sk, SOCK_ZAPPED);
 
-		if ((dev = rose_dev_first()) == NULL) {
+		dev = rose_dev_first();
+		if (!dev) {
 			err = -ENETUNREACH;
 			goto out_release;
 		}
@@ -788,6 +794,7 @@ static int rose_connect(struct socket *sock, struct sockaddr *uaddr, int addr_le
 		user = ax25_findbyuid(current_euid());
 		if (!user) {
 			err = -EINVAL;
+			dev_put(dev);
 			goto out_release;
 		}
 

net/rose/rose_route.c

@@ -615,6 +615,8 @@ struct net_device *rose_dev_first(void)
 			if (first == NULL || strncmp(dev->name, first->name, 3) < 0)
 				first = dev;
 	}
+	if (first)
+		dev_hold(first);
 	rcu_read_unlock();
 
 	return first;