Re: [PATCH] drm/amdkfd: Fix potential deallocation of previously deallocated memory.

[Andi Shyti]

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@xxxxxxxxxx>
> ---
>  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