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Message-ID: <6b6318ed-cd45-203c-d05d-2b5437213656@intel.com>
Date:   Fri, 6 May 2022 18:50:16 +0200
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Subject: Re: [PATCH] fbdev: efifb: Fix a use-after-free due early fb_info
 cleanup
Content-Language: en-US
To:     Javier Martinez Canillas <javierm@redhat.com>,
        <linux-kernel@vger.kernel.org>
CC:     =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= <ville.syrjala@linux.intel.com>,
        <intel-gfx@lists.freedesktop.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Helge Deller <deller@gmx.de>, Peter Jones <pjones@redhat.com>,
        "Thomas Zimmermann" <tzimmermann@suse.de>,
        <dri-devel@lists.freedesktop.org>, <linux-fbdev@vger.kernel.org>
References: <20220506132225.588379-1-javierm@redhat.com>
From:   Andrzej Hajda <andrzej.hajda@intel.com>
Organization: Intel Technology Poland sp. z o.o. - ul. Slowackiego 173, 80-298
 Gdansk - KRS 101882 - NIP 957-07-52-316
In-Reply-To: <20220506132225.588379-1-javierm@redhat.com>
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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 = {