linux-kernel - Re: [PATCH] drm/nouveau: fix a use-after-free in nouveau_gem_prime_import_sg

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Date:   Thu, 07 Jul 2022 15:49:11 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Jianglei Nie <niejianglei2021@....com>, bskeggs@...hat.com,
        kherbst@...hat.com, airlied@...ux.ie, daniel@...ll.ch
Cc:     dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/nouveau: fix a use-after-free in
 nouveau_gem_prime_import_sg_table()

Reviewed-by: Lyude Paul <lyude@...hat.com>

Will push to the appropriate branch in a moment

On Tue, 2022-07-05 at 21:25 +0800, Jianglei Nie wrote:
> nouveau_bo_init() is backed by ttm_bo_init() and ferries its return code
> back to the caller. On failures, ttm will call nouveau_bo_del_ttm() and
> free the memory.Thus, when nouveau_bo_init() returns an error, the gem
> object has already been released. Then the call to nouveau_bo_ref() will
> use the freed "nvbo->bo" and lead to a use-after-free bug.
> 
> We should delete the call to nouveau_bo_ref() to avoid the use-after-free.
> 
> Signed-off-by: Jianglei Nie <niejianglei2021@....com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_prime.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_prime.c
> b/drivers/gpu/drm/nouveau/nouveau_prime.c
> index 347488685f74..9608121e49b7 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_prime.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_prime.c
> @@ -71,7 +71,6 @@ struct drm_gem_object
> *nouveau_gem_prime_import_sg_table(struct drm_device *dev,
>         ret = nouveau_bo_init(nvbo, size, align, NOUVEAU_GEM_DOMAIN_GART,
>                               sg, robj);
>         if (ret) {
> -               nouveau_bo_ref(NULL, &nvbo);
>                 obj = ERR_PTR(ret);
>                 goto unlock;
>         }

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat