Re: [PATCH] fbdev: efifb: Fix a use-after-free due early fb_info cleanup

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

On 06.05.2022 15:22, Javier Martinez Canillas wrote:
> Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
> than .remove") attempted to fix a use-after-free error due driver freeing
> the fb_info in the .remove handler instead of doing it in .fb_destroy.
>
> But ironically that change introduced yet another use-after-free since the
> fb_info was still used after the free.
>
> This should fix for good by freeing the fb_info at the end of the handler.
>
> Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")
> Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Reported-by: Andrzej Hajda <andrzej.hajda@intel.com>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> ---

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

Regards
Andrzej
>
>   drivers/video/fbdev/efifb.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index cfa3dc0b4eee..b3d5f884c544 100644
> --- a/drivers/video/fbdev/efifb.c
> +++ b/drivers/video/fbdev/efifb.c
> @@ -259,12 +259,12 @@ static void efifb_destroy(struct fb_info *info)
>   			memunmap(info->screen_base);
>   	}
>   
> -	framebuffer_release(info);
> -
>   	if (request_mem_succeeded)
>   		release_mem_region(info->apertures->ranges[0].base,
>   				   info->apertures->ranges[0].size);
>   	fb_dealloc_cmap(&info->cmap);
> +
> +	framebuffer_release(info);
>   }
>   
>   static const struct fb_ops efifb_ops = {