Re: [Intel-gfx] [PATCH 22/22] drm: Use drm_mode_copy()

[Andrzej Hajda <andrzej.hajda@intel.com>]

On 18.02.2022 11:04, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> struct drm_display_mode embeds a list head, so overwriting
> the full struct with another one will corrupt the list
> (if the destination mode is on a list). Use drm_mode_copy()
> instead which explicitly preserves the list head of
> the destination mode.
> 
> Even if we know the destination mode is not on any list
> using drm_mode_copy() seems decent as it sets a good
> example. Bad examples of not using it might eventually
> get copied into code where preserving the list head
> actually matters.
> 
> Obviously one case not covered here is when the mode
> itself is embedded in a larger structure and the whole
> structure is copied. But if we are careful when copying
> into modes embedded in structures I think we can be a
> little more reassured that bogus list heads haven't been
> propagated in.
> 
> @is_mode_copy@
> @@
> drm_mode_copy(...)
> {
> ...
> }
> 
> @depends on !is_mode_copy@
> struct drm_display_mode *mode;
> expression E, S;
> @@
> (
> - *mode = E
> + drm_mode_copy(mode, &E)
> |
> - memcpy(mode, E, S)
> + drm_mode_copy(mode, E)
> )
> 
> @depends on !is_mode_copy@
> struct drm_display_mode mode;
> expression E;
> @@
> (
> - mode = E
> + drm_mode_copy(&mode, &E)
> |
> - memcpy(&mode, E, S)
> + drm_mode_copy(&mode, E)
> )
> 
> @@
> struct drm_display_mode *mode;
> @@
> - &*mode
> + mode
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---

Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>

Regards
Andrzej