Re: [PATCH 2/2] soundwire: qcom: gracefully handle too many ports in DT

[Konrad Dybcio]

On 22.02.2023 15:44, Krzysztof Kozlowski wrote:
> There are two issues related to the number of ports coming from
> Devicetree when exceeding in total QCOM_SDW_MAX_PORTS.  Both lead to
> incorrect memory accesses:
> 1. With DTS having too big value of input or output ports, the driver,
>    when copying port parameters from local/stack arrays into 'pconfig'
>    array in 'struct qcom_swrm_ctrl', will iterate over their sizes.
> 
> 2. If DTS also has too many parameters for these ports (e.g.
>    qcom,ports-sinterval-low), the driver will overflow buffers on the
>    stack when reading these properties from DTS.
> 
> Add a sanity check so incorrect DTS will not cause kernel memory
> corruption.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> ---
Fixes: 02efb49aa805 ("soundwire: qcom: add support for SoundWire controller")

Reviewed-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>

Konrad
>  drivers/soundwire/qcom.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
> index 79bebcecde6d..c296e0bf897b 100644
> --- a/drivers/soundwire/qcom.c
> +++ b/drivers/soundwire/qcom.c
> @@ -1218,6 +1218,9 @@ static int qcom_swrm_get_port_config(struct qcom_swrm_ctrl *ctrl)
>  	ctrl->num_dout_ports = val;
>  
>  	nports = ctrl->num_dout_ports + ctrl->num_din_ports;
> +	if (nports > QCOM_SDW_MAX_PORTS)
> +		return -EINVAL;
> +
>  	/* Valid port numbers are from 1-14, so mask out port 0 explicitly */
>  	set_bit(0, &ctrl->dout_port_mask);
>  	set_bit(0, &ctrl->din_port_mask);