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References: <20200821061643.16278-1-sonnysasaka@chromium.org>
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From:   Sonny Sasaka <sonnysasaka@chromium.org>
Date:   Wed, 16 Sep 2020 15:38:15 -0700
Message-ID: <CAO271m=UWgjM1nLWzrwfvG4r3V7c6wdPDJk7EvRtW4cgsLXqhg@mail.gmail.com>
Subject: Re: [PATCH BlueZ 1/2] gatt: StartNotify is not allowed when device is disconnecting
To:     BlueZ <linux-bluetooth@vger.kernel.org>
Cc:     Joseph Hwang <josephsih@chromium.org>
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Dear BlueZ maintainers,

Friendly ping to review this patch. Thanks!


On Thu, Aug 20, 2020 at 11:17 PM Sonny Sasaka <sonnysasaka@chromium.org> wrote:
>
> From: Joseph Hwang <josephsih@chromium.org>
>
> This patch fixed a bluetoothd crash in register_notify_cb(). The
> crash is incurred by an exception that under some situation, a
> characteristic may be freed when register_notify_cb() is invoked.
>
> When a device is disconnecting, the device interface would hold valid
> for a while until the disconnection procedure between the client and
> the server is completed. If another process happens to request to start
> notification of a characteristic on the disconnecting device, it may
> incur a problem. In this case, the client would still send the
> StartNotify request since the characteristic object is still valid.
> However, the characteristic may be freed soon and become invalid
> when the corresponding callback function is invoked later. This
> leads to the bluetoothd crash due to the segmentation fault.
>
> To handle the exception, if another process requests to start
> notification when the device is disconnecting, it should reject the
> request.
>
> Tested on Chrome OS that this patch fixes bluetoothd crash in
> register_notify_cb().
>
> ---
>  src/gatt-client.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/src/gatt-client.c b/src/gatt-client.c
> index 20c3fbec2..c706307c7 100644
> --- a/src/gatt-client.c
> +++ b/src/gatt-client.c
> @@ -1545,6 +1545,12 @@ static DBusMessage *characteristic_start_notify(DBusConnection *conn,
>         const char *sender = dbus_message_get_sender(msg);
>         struct async_dbus_op *op;
>         struct notify_client *client;
> +       struct btd_device *device = chrc->service->client->device;
> +
> +       if (device_is_disconnecting(device)) {
> +               error("Device is disconnecting. StartNotify is not allowed.");
> +               return btd_error_not_connected(msg);
> +       }
>
>         if (chrc->notify_io)
>                 return btd_error_not_permitted(msg, "Notify acquired");
> --
> 2.26.2
>