Subject: Re: [RFC/PATCH] Bluetooth: prevent double l2cap_chan_destroy

From: Chanyeol Park <[email-masked]>
Date: Tue, 22 May 2012 21:23:32 +0900

Hi

On 2012년 05월 22일 11:50, Minho Ban wrote:
> @@ -1343,10 +1343,10 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
>                  l2cap_chan_lock(chan);
>
>                  l2cap_chan_del(chan, err);
> +               chan->ops->close(chan->data);
>
>                  l2cap_chan_unlock(chan);
>
> -               chan->ops->close(chan->data);
>                  l2cap_chan_put(chan);
>          }
I think this patch does not make sense Because inside chan->ops->close() 
"chan" could be freed in the l2cap_chan_destroy().

> close callback must locate within chan_lock unless it can be scheduled to other thread
> which may wait for chan_lock in l2cap_sock_shutdown and this lead to duplicate sock_kill.
>
>   static void l2cap_sock_kill(struct sock *sk)
>   {
> -       if (!sock_flag(sk, SOCK_ZAPPED) || sk->sk_socket)
> +       if (!sock_flag(sk, SOCK_ZAPPED) || sock_flag(sk, SOCK_DEAD) ||
> +                       sk->sk_socket)
>                  return;
>
>          BT_DBG("sk %p state %s", sk, state_to_string(sk->sk_state));
>
> Duplicate sock_kill may happen anyway, need test SOCK_DEAD if chan_destroy is already called.
Even l2cap_sock_kill() is called twice, " if (!sock_flag(sk, 
SOCK_ZAPPED) || sk->sk_socket)" can't filter it.
I tested Mr.ban case. it works fine with me.

BR
Chanyeol Park.