[PATCH] drm/stm: ltdc: limit number of layer to avoid memory overflow

[Philippe CORNU]

Dear Yannick,
Thank you for your patch,

Acked-by: Philippe Cornu <philippe.cornu at st.com>

Philippe :)

On 4/3/19 11:20 AM, Yannick Fertré wrote:
> If the number of layer is greater than LTDC_MAX_LAYER, we can have
> memory overflow when reading plane_fpsi[].
> 
> Signed-off-by: Yannick Fertré <yannick.fertre at st.com>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 32fd6a3..05bd4b6 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -1021,10 +1021,13 @@ static int ltdc_get_caps(struct drm_device *ddev)
>   	struct ltdc_device *ldev = ddev->dev_private;
>   	u32 bus_width_log2, lcr, gc2r;
>   
> -	/* at least 1 layer must be managed */
> +	/*
> +	 * at least 1 layer must be managed & the number of layers
> +	 * must not exceed LTDC_MAX_LAYER
> +	 */
>   	lcr = reg_read(ldev->regs, LTDC_LCR);
>   
> -	ldev->caps.nb_layers = max_t(int, lcr, 1);
> +	ldev->caps.nb_layers = clamp((int)lcr, 1, LTDC_MAX_LAYER);
>   
>   	/* set data bus width */
>   	gc2r = reg_read(ldev->regs, LTDC_GC2R);
>