linux-kernel - Re: [PATCH v2] Bluetooth: skip invalid hci_sync_conn_complete

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Message-Id: <72819085-5564-4386-AD94-2901083CDE65@holtmann.org>
Date:   Thu, 29 Jul 2021 13:38:50 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        skhan@...uxfoundation.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+66264bf2fd0476be7e6c@...kaller.appspotmail.com
Subject: Re: [PATCH v2] Bluetooth: skip invalid hci_sync_conn_complete_evt

Hi Desmond,

> Syzbot reported a corrupted list in kobject_add_internal [1]. This
> happens when multiple HCI_EV_SYNC_CONN_COMPLETE event packets with
> status 0 are sent for the same HCI connection. This causes us to
> register the device more than once which corrupts the kset list.
> 
> As this is forbidden behavior, we add a check for whether we're
> trying to process the same HCI_EV_SYNC_CONN_COMPLETE event multiple
> times for one connection. If that's the case, the event is invalid, so
> we report an error that the device is misbehaving, and ignore the
> packet.
> 
> Link: https://syzkaller.appspot.com/bug?extid=66264bf2fd0476be7e6c [1]
> Reported-by: syzbot+66264bf2fd0476be7e6c@...kaller.appspotmail.com
> Tested-by: syzbot+66264bf2fd0476be7e6c@...kaller.appspotmail.com
> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
> ---
> 
> v1 -> v2:
> - Added more comments to explain the reasoning behind the new check, and
> a bt_dev_err message upon detecting the invalid event. As suggested by
> Marcel Holtmann.
> 
> net/bluetooth/hci_event.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)

I shortened the error message and then applied your patch to bluetooth-next tree.

Regards

Marcel