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Date:   Tue, 18 Apr 2023 10:47:18 +0200
From:   Andi Shyti <andi.shyti@linux.intel.com>
To:     Daniil Dulov <d.dulov@aladdin.ru>
Cc:     Felix Kuehling <Felix.Kuehling@amd.com>,
        lvc-project@linuxtesting.org, David Airlie <airlied@linux.ie>,
        linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org,
        dri-devel@lists.freedesktop.org,
        Alex Deucher <alexander.deucher@amd.com>,
        Oak Zeng <ozeng@amd.com>,
        Christian =?iso-8859-15?Q?K=F6nig?= <christian.koenig@amd.com>
Subject: Re: [PATCH] drm/amdkfd: Fix potential deallocation of previously
 deallocated memory.
Message-ID: <ZD5ZFoEk92MNQpqD@ashyti-mobl2.lan>
References: <20230418065521.453001-1-d.dulov@aladdin.ru>
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In-Reply-To: <20230418065521.453001-1-d.dulov@aladdin.ru>
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Hi Daniil,

On Mon, Apr 17, 2023 at 11:55:21PM -0700, Daniil Dulov wrote:
> Pointer mqd_mem_obj can be deallocated in kfd_gtt_sa_allocate().
> The function then returns non-zero value, which causes the second deallocation.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: d1f8f0d17d40 ("drm/amdkfd: Move non-sdma mqd allocation out of init_mqd")
> Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> index 3b6f5963180d..bce11c5b07d6 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> @@ -119,7 +119,8 @@ static struct kfd_mem_obj *allocate_mqd(struct kfd_dev *kfd,
>  	}
>  
>  	if (retval) {
> -		kfree(mqd_mem_obj);
> +		if (mqd_mem_obj)
> +			kfree(mqd_mem_obj);

I think this is not needed. kfree() returns immediately if
mqd_mem_obj is NULL.

Andi

>  		return NULL;
>  	}
>  
> -- 
> 2.25.1