linux-kernel - Re: [PATCH v2] drm/radeon: fix race condition UAF in radeon_gem_set_domain

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Date:   Mon, 5 Jun 2023 10:12:52 +0200
From:   Christian König <christian.koenig@....com>
To:     Min Li <lm0963hack@...il.com>, alexander.deucher@....com
Cc:     Xinhui.Pan@....com, airlied@...il.com, daniel@...ll.ch,
        sumit.semwal@...aro.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v2] drm/radeon: fix race condition UAF in
 radeon_gem_set_domain_ioctl

Am 03.06.23 um 09:43 schrieb Min Li:
> Userspace can race to free the gobj(robj converted from), robj should not
> be accessed again after drm_gem_object_put, otherwith it will result in
> use-after-free.
>
> Signed-off-by: Min Li <lm0963hack@...il.com>

Reviewed-by: Christian König <christian.koenig@....com>

> ---
> Changes in v2:
> - Remove unused robj, avoid compile complain
>
>   drivers/gpu/drm/radeon/radeon_gem.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
> index bdc5af23f005..d3f5ddbc1704 100644
> --- a/drivers/gpu/drm/radeon/radeon_gem.c
> +++ b/drivers/gpu/drm/radeon/radeon_gem.c
> @@ -459,7 +459,6 @@ int radeon_gem_set_domain_ioctl(struct drm_device *dev, void *data,
>   	struct radeon_device *rdev = dev->dev_private;
>   	struct drm_radeon_gem_set_domain *args = data;
>   	struct drm_gem_object *gobj;
> -	struct radeon_bo *robj;
>   	int r;
>   
>   	/* for now if someone requests domain CPU -
> @@ -472,13 +471,12 @@ int radeon_gem_set_domain_ioctl(struct drm_device *dev, void *data,
>   		up_read(&rdev->exclusive_lock);
>   		return -ENOENT;
>   	}
> -	robj = gem_to_radeon_bo(gobj);
>   
>   	r = radeon_gem_set_domain(gobj, args->read_domains, args->write_domain);
>   
>   	drm_gem_object_put(gobj);
>   	up_read(&rdev->exclusive_lock);
> -	r = radeon_gem_handle_lockup(robj->rdev, r);
> +	r = radeon_gem_handle_lockup(rdev, r);
>   	return r;
>   }
>