On Tue, Mar 25, 2025 at 01:24:09PM -0400, Anusha Srivatsa wrote:
> Allocate panel via reference counting.
> Add _get() and _put() helper functions
> to ensure panel allocations are refcounted.
> Avoid use after free by ensuring panel is
> valid and can be usable till the last reference
> is put. This avoids use-after-free
>
> Signed-off-by: Anusha Srivatsa <asriv...@redhat.com>
> ---
> drivers/gpu/drm/drm_panel.c | 65
> ++++++++++++++++++++++++++++++++++++++++++++-
> include/drm/drm_panel.h | 19 ++++++++++++-
> 2 files changed, 82 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> index
> bdeab5710ee324dc1742fbc77582250960556308..079c3c666a2ddc99a0051d1a3c9ba65d986dd003
> 100644
> --- a/drivers/gpu/drm/drm_panel.c
> +++ b/drivers/gpu/drm/drm_panel.c
> @@ -355,24 +355,87 @@ struct drm_panel *of_drm_find_panel(const struct
> device_node *np)
> }
> EXPORT_SYMBOL(of_drm_find_panel);
>
> +static void __drm_panel_free(struct kref *kref)
> +{
> + struct drm_panel *panel = container_of(kref, struct drm_panel,
> refcount);
> +
> + kfree(panel->container);
> +}
> +
> +/**
> + * drm_panel_get - Acquire a panel reference
> + * @panel: DRM panel
> + *
> + * This function increments the panel's refcount.
> + *
> + */
> +struct drm_panel *drm_panel_get(struct drm_panel *panel)
> +{
> + if (!panel)
> + return panel;
> +
> + kref_get(&panel->refcount);
> +
> + return panel;
> +}
This should be exported
> +/**
> + * drm_panel_put - Release a panel reference
> + * @panel: DRM panel
> + *
> + * This function decrements the panel's reference count and frees the
> + * object if the reference count drops to zero.
> + */
> +struct drm_panel *drm_panel_put(struct drm_panel *panel)
> +{
> + if (!panel)
> + return panel;
> +
> + kref_put(&panel->refcount, __drm_panel_free);
> +
> + return panel;
> +}
Ditto,
> +/**
> + * drm_bridge_put_void - wrapper to drm_bridge_put() taking a void pointer
> + *
> + * @data: pointer to @struct drm_bridge, cast to a void pointer
> + *
> + * Wrapper of drm_bridge_put() to be used when a function taking a void
> + * pointer is needed, for example as a devm action.
> + */
> +static void drm_panel_put_void(void *data)
> +{
> + struct drm_panel *panel = (struct drm_panel *)data;
> +
> + drm_panel_put(panel);
> +}
You can drop the documentation on that one.
Looks good otherwise,
Maxime
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