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

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Date:   Thu, 1 Jun 2023 16:34:01 +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] drm/radeon: fix race condition UAF in
 radeon_gem_set_domain_ioctl

Am 26.05.23 um 14:37 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>
> ---
>   drivers/gpu/drm/radeon/radeon_gem.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
> index bdc5af23f005..450c7cbdd28a 100644
> --- a/drivers/gpu/drm/radeon/radeon_gem.c
> +++ b/drivers/gpu/drm/radeon/radeon_gem.c
> @@ -478,7 +478,7 @@ int radeon_gem_set_domain_ioctl(struct drm_device *dev, void *data,
>   
>   	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);

This also makes the robj unused which the kernel test robot also 
complained about.

Please remove that local variable and re-submit.

Apart from that the patch looks good to me,
Christian.

>   	return r;
>   }
>