linux-kernel - Re: [PATCH 3/3] drm/vmwgfx: fix potential UAF in vmwgfx

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Message-ID: <YPlK9b+7CN533jpl@phenom.ffwll.local>
Date:   Thu, 22 Jul 2021 12:39:49 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
Cc:     linux-graphics-maintainer@...are.com, zackr@...are.com,
        airlied@...ux.ie, daniel@...ll.ch,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        skhan@...uxfoundation.org, gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH 3/3] drm/vmwgfx: fix potential UAF in vmwgfx_surface.c

On Thu, Jul 22, 2021 at 05:29:29PM +0800, Desmond Cheong Zhi Xi wrote:
> drm_file.master should be protected by either drm_device.master_mutex
> or drm_file.master_lookup_lock when being dereferenced. However,
> drm_master_get is called on unprotected file_priv->master pointers in
> vmw_surface_define_ioctl and vmw_gb_surface_define_internal.
> 
> This is fixed by replacing drm_master_get with drm_file_get_master.
> 
> Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

I'll let Zack take a look at this and expect him to push this patch to
drm-misc.git.
-Daniel

> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> index 0eba47762bed..5d53a5f9d123 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
> @@ -865,7 +865,7 @@ int vmw_surface_define_ioctl(struct drm_device *dev, void *data,
>  	user_srf->prime.base.shareable = false;
>  	user_srf->prime.base.tfile = NULL;
>  	if (drm_is_primary_client(file_priv))
> -		user_srf->master = drm_master_get(file_priv->master);
> +		user_srf->master = drm_file_get_master(file_priv);
>  
>  	/**
>  	 * From this point, the generic resource management functions
> @@ -1534,7 +1534,7 @@ vmw_gb_surface_define_internal(struct drm_device *dev,
>  
>  	user_srf = container_of(srf, struct vmw_user_surface, srf);
>  	if (drm_is_primary_client(file_priv))
> -		user_srf->master = drm_master_get(file_priv->master);
> +		user_srf->master = drm_file_get_master(file_priv);
>  
>  	res = &user_srf->srf.res;
>  
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch