linux-kernel - Re: [PATCH] drm/via: Add new condition to via_dma

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Message-ID: <YxeengBAncBqNab0@phenom.ffwll.local>
Date:   Tue, 6 Sep 2022 21:25:18 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Alisa Khabibrakhmanova <khabibrakhmanova@...ras.ru>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        ldv-project@...uxtesting.org
Subject: Re: [PATCH] drm/via: Add new condition to via_dma_cleanup()

On Fri, Jul 29, 2022 at 12:06:43PM +0300, Alisa Khabibrakhmanova wrote:
> Pointer dev_priv->mmio, which was checked for NULL at via_do_init_map(),
> is passed to via_do_cleanup_map() and is dereferenced there without check.
> 
> The patch adds the condition in via_dma_cleanup() which prevents potential NULL
> pointer dereference.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: 22f579c621e2 ("drm: Add via unichrome support")
> Signed-off-by: Alisa Khabibrakhmanova <khabibrakhmanova@...ras.ru>

This seems to have fallen through cracks, I applied it to drm-misc-next
now.

Thanks for your patch.
-Daniel

> ---
>  drivers/gpu/drm/via/via_dri1.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/via/via_dri1.c b/drivers/gpu/drm/via/via_dri1.c
> index d695d9291ece..691e3ceb0062 100644
> --- a/drivers/gpu/drm/via/via_dri1.c
> +++ b/drivers/gpu/drm/via/via_dri1.c
> @@ -2961,7 +2961,7 @@ int via_dma_cleanup(struct drm_device *dev)
>  		drm_via_private_t *dev_priv =
>  		    (drm_via_private_t *) dev->dev_private;
>  
> -		if (dev_priv->ring.virtual_start) {
> +		if (dev_priv->ring.virtual_start && dev_priv->mmio) {
>  			via_cmdbuf_reset(dev_priv);
>  
>  			drm_legacy_ioremapfree(&dev_priv->ring.map, dev);
> -- 
> 2.34.1
> 

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