Re: [PATCH 2/3] drm/ingenic: Register devm action to cleanup encoders

From: Laurent Pinchart
Date: Mon Jan 18 2021 - 05:18:43 EST


Hi Paul,

Thank you for the patch.

On Sun, Jan 17, 2021 at 11:26:45AM +0000, Paul Cercueil wrote:
> Since the encoders have been devm-allocated, they will be freed way
> before drm_mode_config_cleanup() is called. To avoid use-after-free
> conditions, we then must ensure that drm_encoder_cleanup() is called
> before the encoders are freed.

How about allocating the encoder with drmm_encoder_alloc() instead ?

> Fixes: c369cb27c267 ("drm/ingenic: Support multiple panels/bridges")
> Cc: <stable@xxxxxxxxxxxxxxx> # 5.8+
> Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> index 368bfef8b340..d23a3292a0e0 100644
> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
> @@ -803,6 +803,11 @@ static void __maybe_unused ingenic_drm_release_rmem(void *d)
> of_reserved_mem_device_release(d);
> }
>
> +static void ingenic_drm_encoder_cleanup(void *encoder)
> +{
> + drm_encoder_cleanup(encoder);
> +}
> +
> static int ingenic_drm_bind(struct device *dev, bool has_components)
> {
> struct platform_device *pdev = to_platform_device(dev);
> @@ -1011,6 +1016,11 @@ static int ingenic_drm_bind(struct device *dev, bool has_components)
> return ret;
> }
>
> + ret = devm_add_action_or_reset(dev, ingenic_drm_encoder_cleanup,
> + encoder);
> + if (ret)
> + return ret;
> +
> ret = drm_bridge_attach(encoder, bridge, NULL, 0);
> if (ret) {
> dev_err(dev, "Unable to attach bridge\n");

--
Regards,

Laurent Pinchart