From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chanyeol Park <chanyeol.park@samsung.com>
Subject: Re: [RFC/PATCH] Bluetooth: prevent double l2cap_chan_destroy
Date: Tue, 22 May 2012 21:23:32 +0900
Message-ID: <4FBB8544.3040408@samsung.com>
References: <4FB992C8.8090105@samsung.com> <20120521162137.GE16942@joana>
 <4FBAFEF5.2000207@samsung.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8;
	format=flowed
Content-Transfer-Encoding: QUOTED-PRINTABLE
Cc: Gustavo Padovan <gustavo@padovan.org>,
	Marcel Holtmann <marcel@holtmann.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
To: Minho Ban <mhban@samsung.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-reply-to: <4FBAFEF5.2000207@samsung.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: netdev.vger.kernel.org

Hi

On 2012=EB=85=84 05=EC=9B=94 22=EC=9D=BC 11:50, Minho Ban wrote:
> @@ -1343,10 +1343,10 @@ static void l2cap_conn_del(struct hci_conn *h=
con, 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(=
)=20
"chan" could be freed in the l2cap_chan_destroy().

> close callback must locate within chan_lock unless it can be schedule=
d 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_de=
stroy is already called.
Even l2cap_sock_kill() is called twice, " if (!sock_flag(sk,=20
SOCK_ZAPPED) || sk->sk_socket)" can't filter it.
I tested Mr.ban case. it works fine with me.

BR
Chanyeol Park.