Re: [PATCH] drm/nouveau/disp: fix use-after-free in error handling of nouveau_connector_create

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>

On Mon, 2023-08-14 at 16:49 +0200, Karol Herbst wrote:
> We can't simply free the connector after calling drm_connector_init on it.
> We need to clean up the drm side first.
> 
> It might not fix all regressions from 2b5d1c29f6c4 ("drm/nouveau/disp:
> PIOR DP uses GPIO for HPD, not PMGR AUX interrupts"), but at least it
> fixes a memory corruption in error handling related to that commit.
> 
> Link: https://lore.kernel.org/lkml/20230806213107.GFZNARG6moWpFuSJ9W@fat_crate.local/
> Fixes: 95983aea8003 ("drm/nouveau/disp: add connector class")
> Signed-off-by: Karol Herbst <kherbst@xxxxxxxxxx>
> ---
>  drivers/gpu/drm/nouveau/nouveau_connector.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c b/drivers/gpu/drm/nouveau/nouveau_connector.c
> index a2e0033e8a260..622f6eb9a8bfd 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_connector.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
> @@ -1408,8 +1408,7 @@ nouveau_connector_create(struct drm_device *dev,
>  		ret = nvif_conn_ctor(&disp->disp, nv_connector->base.name, nv_connector->index,
>  				     &nv_connector->conn);
>  		if (ret) {
> -			kfree(nv_connector);
> -			return ERR_PTR(ret);
> +			goto drm_conn_err;
>  		}
>  
>  		ret = nvif_conn_event_ctor(&nv_connector->conn, "kmsHotplug",
> @@ -1426,8 +1425,7 @@ nouveau_connector_create(struct drm_device *dev,
>  			if (ret) {
>  				nvif_event_dtor(&nv_connector->hpd);
>  				nvif_conn_dtor(&nv_connector->conn);
> -				kfree(nv_connector);
> -				return ERR_PTR(ret);
> +				goto drm_conn_err;
>  			}
>  		}
>  	}
> @@ -1475,4 +1473,9 @@ nouveau_connector_create(struct drm_device *dev,
>  
>  	drm_connector_register(connector);
>  	return connector;
> +
> +drm_conn_err:
> +	drm_connector_cleanup(connector);
> +	kfree(nv_connector);
> +	return ERR_PTR(ret);
>  }

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat