Re: [PATCH] drm/nouveau: avoid null deref on bad arguments to nouveau_vma_getmap

["Pasi Kärkkäinen" <pasik-X3B1VOXEql0@public.gmane.org>]

On Thu, Aug 22, 2013 at 09:12:40AM +0200, Maarten Lankhorst wrote:
> Op 22-08-13 02:10, Ilia Mirkin schreef:
> > The code expects non-VRAM mem nodes to have a pages list. If that's not
> > set, it will do a null deref down the line. Warn on that condition and
> > return an error.
> >
> > See https://bugs.freedesktop.org/show_bug.cgi?id=64774
> >
> > Reported-by: Pasi Kärkkäinen <pasik-X3B1VOXEql0@public.gmane.org>
> > Tested-by: Pasi Kärkkäinen <pasik-X3B1VOXEql0@public.gmane.org>
> > Signed-off-by: Ilia Mirkin <imirkin-FrUbXkNCsVf2fBVCVOL8/A@public.gmane.org>
> > Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> # 3.8+
> > ---
> >
> > I don't exactly understand what's going on, but this is just a
> > straightforward way to avoid a null deref that you see happens in the
> > bug. I haven't figured out the root cause of this, but it's getting
> > well into the "I have no idea how TTM works" space. However this seems
> > like a bit of defensive programming -- nouveau_vm_map_sg will pass
> > node->pages as a list down, which will be dereferenced by
> > nvc0_vm_map_sg. Perhaps the other arguments should make that
> > dereferencing not happen, but it definitely was happening here, as you
> > can see in the bug.
> >
> > Ben/Maarten, I'll let you judge whether this check is appropriate,
> > since like I hope I was able to convey above, I'm just not really sure :)
> Not it really isn't appropriate..
> 
> You'd have to call call nouveau_vm_map_sg_table instead, the only place that doesn't handle that correctly
> is where it's not expected to be called.
> 
> Here, have a completely untested patch to fix things...
>

Thanks! I'll give it a try later today.. 


-- Pasi
 

> diff --git a/drivers/gpu/drm/nouveau/nouveau_display.c b/drivers/gpu/drm/nouveau/nouveau_display.c
> --- a/drivers/gpu/drm/nouveau/nouveau_display.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_display.c
> @@ -138,17 +143,26 @@ nouveau_user_framebuffer_create(struct drm_device *dev,
>  {
>  	struct nouveau_framebuffer *nouveau_fb;
>  	struct drm_gem_object *gem;
> +	struct nouveau_bo *nvbo;
>  	int ret = -ENOMEM;
>  
>  	gem = drm_gem_object_lookup(dev, file_priv, mode_cmd->handles[0]);
>  	if (!gem)
>  		return ERR_PTR(-ENOENT);
>  
> +	nvbo = nouveau_gem_object(gem);
> +	if (!(nvbo->valid_domains & NOUVEAU_GEM_DOMAIN_VRAM)) {
> +		nv_warn(nouveau_drm(dev), "Trying to create a fb in vram with"
> +			" valid_domains=%08x\n", nvbo->valid_domains);
> +		ret = -EINVAL;
> +		goto err_unref;
> +	}
> +
>  	nouveau_fb = kzalloc(sizeof(struct nouveau_framebuffer), GFP_KERNEL);
>  	if (!nouveau_fb)
>  		goto err_unref;
>  
> -	ret = nouveau_framebuffer_init(dev, nouveau_fb, mode_cmd, nouveau_gem_object(gem));
> +	ret = nouveau_framebuffer_init(dev, nouveau_fb, mode_cmd, nvbo);
>  	if (ret)
>  		goto err;
>  
> 
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