Re: [PATCH net] ax25: Fix refcount leak issues of ax25_dev
From: duoming
Date: Wed May 08 2024 - 21:40:49 EST
On Tue, 7 May 2024 11:08:14 +0300 Dan Carpenter wrote:
> diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
> index 9169efb2f43a..4d1ab296d52c 100644
> --- a/net/ax25/af_ax25.c
> +++ b/net/ax25/af_ax25.c
> @@ -92,6 +92,7 @@ static void ax25_kill_by_device(struct net_device *dev)
> spin_unlock_bh(&ax25_list_lock);
> ax25_disconnect(s, ENETUNREACH);
> s->ax25_dev = NULL;
> + ax25_dev_put(ax25_dev);
> ax25_cb_del(s);
> spin_lock_bh(&ax25_list_lock);
> goto again;
> @@ -101,11 +102,8 @@ static void ax25_kill_by_device(struct net_device *dev)
> lock_sock(sk);
> ax25_disconnect(s, ENETUNREACH);
> s->ax25_dev = NULL;
> - if (sk->sk_socket) {
> - netdev_put(ax25_dev->dev,
> - &s->dev_tracker);
> - ax25_dev_put(ax25_dev);
> - }
> + netdev_put(ax25_dev->dev, &s->dev_tracker);
> + ax25_dev_put(ax25_dev);
We should not decrease the refcount without checking "if (sk->sk_socket)", because
there is a race condition between ax25_kill_by_device() and ax25_release(), if we
decrease the refcount in ax25_release(), we should not decrease it here, otherwise
the refcount underflow will happen.
Best regards,
Duoming Zhou