linux-kernel - Re: [PATCH v5] Bluetooth: Fix l2cap_disconnect

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Date:   Wed, 31 May 2023 18:28:08 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     Ying Hsu <yinghsu@...omium.org>
Cc:     linux-bluetooth@...r.kernel.org,
        chromeos-bluetooth-upstreaming@...omium.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v5] Bluetooth: Fix l2cap_disconnect_req deadlock

On Wed, May 31, 2023 at 03:44:56AM +0000, Ying Hsu wrote:
> L2CAP assumes that the locks conn->chan_lock and chan->lock are
> acquired in the order conn->chan_lock, chan->lock to avoid
> potential deadlock.
> For example, l2sock_shutdown acquires these locks in the order:
>   mutex_lock(&conn->chan_lock)
>   l2cap_chan_lock(chan)
> 
> However, l2cap_disconnect_req acquires chan->lock in
> l2cap_get_chan_by_scid first and then acquires conn->chan_lock
> before calling l2cap_chan_del. This means that these locks are
> acquired in unexpected order, which leads to potential deadlock:
>   l2cap_chan_lock(c)
>   mutex_lock(&conn->chan_lock)
> 
> This patch releases chan->lock before acquiring the conn_chan_lock
> to avoid the potential deadlock.
> 
> Fixes: ("a2a9339e1c9d Bluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}")

nit: this should be

Fixes: a2a9339e1c9d ("Bluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}")

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