Re: [PATCH 8/8] usb: typec: ucsi: validate connector number in ucsi_connector_change()

[Benson Leung <bleung@google.com>]

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On Wed, May 13, 2026 at 05:52:55PM +0200, Greg Kroah-Hartman wrote:
> The connector number in a UCSI CCI notification is a 7-bit field
> supplied by the PPM.  ucsi_connector_change() uses it to index the
> ucsi->connector[] array without checking it against the number of
> connectors the PPM reported at init time, so a buggy or malicious PPM
> (EC firmware, or an I2C-attached UCSI controller on the ccg / stm32g0 /
> glink transports) can drive schedule_work() on memory past the end of
> the array.
> 
> Reject connector numbers that are zero or exceed cap.num_connectors
> before dereferencing the array.
> 
> Assisted-by: gkh_clanker_t1000
> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Cc: Benson Leung <bleung@chromium.org>
> Cc: Jameson Thies <jthies@google.com>
> Cc: Nathan Rebello <nathan.c.rebello@gmail.com>
> Cc: Johan Hovold <johan@kernel.org>
> Cc: Pooja Katiyar <pooja.katiyar@intel.com>
> Cc: Hsin-Te Yuan <yuanhsinte@chromium.org>
> Cc: Abel Vesa <abelvesa@kernel.org>
> Cc: stable <stable@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


Reviewed-by: Benson Leung <bleung@chromium.org>


> ---
>  drivers/usb/typec/ucsi/ucsi.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index 5b7ad9e99cb9..539dc706798d 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -1380,13 +1380,22 @@ static void ucsi_handle_connector_change(struct work_struct *work)
>   */
>  void ucsi_connector_change(struct ucsi *ucsi, u8 num)
>  {
> -	struct ucsi_connector *con = &ucsi->connector[num - 1];
> +	struct ucsi_connector *con;
>  
>  	if (!(ucsi->ntfy & UCSI_ENABLE_NTFY_CONNECTOR_CHANGE)) {
>  		dev_dbg(ucsi->dev, "Early connector change event\n");
>  		return;
>  	}
>  
> +	if (!num || num > ucsi->cap.num_connectors) {
> +		dev_warn_ratelimited(ucsi->dev,
> +				     "Bogus connector change on %u (max %u)\n",
> +				     num, ucsi->cap.num_connectors);
> +		return;
> +	}
> +
> +	con = &ucsi->connector[num - 1];
> +
>  	if (!test_and_set_bit(EVENT_PENDING, &ucsi->flags))
>  		schedule_work(&con->work);
>  }
> -- 
> 2.54.0
> 

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