netdev - Re: [PATCH] l2tp: protect tunnel->del_work by ref

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Date:	Mon, 28 Sep 2015 14:39:44 +0100
From:	James Chapman <jchapman@...alix.com>
To:	Alexander Couzens <lynxis@...0.eu>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] l2tp: protect tunnel->del_work by ref_count

Acked-by: James Chapman <jchapman@...alix.com>


On 28 September 2015 at 10:32, Alexander Couzens <lynxis@...0.eu> wrote:
> There is a small chance that tunnel_free() is called before tunnel->del_work scheduled
> resulting in a zero pointer dereference.
>
> Signed-off-by: Alexander Couzens <lynxis@...0.eu>
> ---
>  net/l2tp/l2tp_core.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
> index f6b090d..afca2eb 100644
> --- a/net/l2tp/l2tp_core.c
> +++ b/net/l2tp/l2tp_core.c
> @@ -1319,7 +1319,7 @@ static void l2tp_tunnel_del_work(struct work_struct *work)
>         tunnel = container_of(work, struct l2tp_tunnel, del_work);
>         sk = l2tp_tunnel_sock_lookup(tunnel);
>         if (!sk)
> -               return;
> +               goto out;
>
>         sock = sk->sk_socket;
>
> @@ -1341,6 +1341,8 @@ static void l2tp_tunnel_del_work(struct work_struct *work)
>         }
>
>         l2tp_tunnel_sock_put(sk);
> +out:
> +       l2tp_tunnel_dec_refcount(tunnel);
>  }
>
>  /* Create a socket for the tunnel, if one isn't set up by
> @@ -1636,8 +1638,13 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
>   */
>  int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
>  {
> +       l2tp_tunnel_inc_refcount(tunnel);
>         l2tp_tunnel_closeall(tunnel);
> -       return (false == queue_work(l2tp_wq, &tunnel->del_work));
> +       if (false == queue_work(l2tp_wq, &tunnel->del_work)) {
> +               l2tp_tunnel_dec_refcount(tunnel);
> +               return 1;
> +       }
> +       return 0;
>  }
>  EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
>
> --
> 2.5.3
>
> --
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