linux-kernel - Re: [PATCH 4.4 49/56] Bluetooth: hci_bcm: add missing tty-device sanity check

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Date:   Wed, 24 May 2017 02:36:55 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Johan Hovold <johan@...nel.org>,
        Marcel Holtmann <marcel@...tmann.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Frederic Danis <frederic.danis@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 4.4 49/56] Bluetooth: hci_bcm: add missing tty-device
 sanity check

On Thu, 2017-05-18 at 12:49 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Johan Hovold <johan@...nel.org>
> 
> commit 95065a61e9bf25fb85295127fba893200c2bbbd8 upstream.
> 
> Make sure to check the tty-device pointer before looking up the sibling
> platform device to avoid dereferencing a NULL-pointer when the tty is
> one end of a Unix98 pty.
> 
> Fixes: 0395ffc1ee05 ("Bluetooth: hci_bcm: Add PM for BCM devices")
> Cc: Frederic Danis <frederic.danis@...ux.intel.com>
> Signed-off-by: Johan Hovold <johan@...nel.org>
> Signed-off-by: Marcel Holtmann <marcel@...tmann.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> ---
>  drivers/bluetooth/hci_bcm.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> --- a/drivers/bluetooth/hci_bcm.c
> +++ b/drivers/bluetooth/hci_bcm.c
> @@ -287,6 +287,9 @@ static int bcm_open(struct hci_uart *hu)
>  
>  	hu->priv = bcm;
>  
> +	if (!hu->tty->dev)
> +		goto out;
> +
>  	mutex_lock(&bcm_device_lock);
>  	list_for_each(p, &bcm_device_list) {
>  		struct bcm_device *dev = list_entry(p, struct bcm_device, list);
> @@ -307,7 +310,7 @@ static int bcm_open(struct hci_uart *hu)
>  	}
>  
>  	mutex_unlock(&bcm_device_lock);
> -
> +out:
>  	return 0;
>  }

I'm a bit sceptical that this is fixing a real bug, but if it is -
surely bcm_open() should fail if the tty device is not the right type?
bcm_setup() would certainly fail after this.

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.