Re: [PATCH 2/2] vdpa/mlx5: Fix possible failure in umem size calculation

[Michael S. Tsirkin]

On Sun, May 30, 2021 at 09:32:14AM +0300, Eli Cohen wrote:
> umem size is a 32 bit unsigned value so assigning it to an int could
> cause false failures. Set the calculated value inside the function and
> modify function name to reflect the fact it updates the size.
> 
> Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
> Signed-off-by: Eli Cohen <elic@xxxxxxxxxx>

could you clarify the impact of the bug please?


> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 53312f0460ad..fdf3e74bffbd 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -610,8 +610,8 @@ static void cq_destroy(struct mlx5_vdpa_net *ndev, u16 idx)
>  	mlx5_db_free(ndev->mvdev.mdev, &vcq->db);
>  }
>  
> -static int umem_size(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int num,
> -		     struct mlx5_vdpa_umem **umemp)
> +static void set_umem_size(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int num,
> +			  struct mlx5_vdpa_umem **umemp)
>  {
>  	struct mlx5_core_dev *mdev = ndev->mvdev.mdev;
>  	int p_a;
> @@ -634,7 +634,7 @@ static int umem_size(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq
>  		*umemp = &mvq->umem3;
>  		break;
>  	}
> -	return p_a * mvq->num_ent + p_b;
> +	(*umemp)->size = p_a * mvq->num_ent + p_b;
>  }
>  
>  static void umem_frag_buf_free(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_umem *umem)
> @@ -650,15 +650,10 @@ static int create_umem(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *m
>  	void *in;
>  	int err;
>  	__be64 *pas;
> -	int size;
>  	struct mlx5_vdpa_umem *umem;
>  
> -	size = umem_size(ndev, mvq, num, &umem);
> -	if (size < 0)
> -		return size;
> -
> -	umem->size = size;
> -	err = umem_frag_buf_alloc(ndev, umem, size);
> +	set_umem_size(ndev, mvq, num, &umem);
> +	err = umem_frag_buf_alloc(ndev, umem, umem->size);
>  	if (err)
>  		return err;
>  
> -- 
> 2.31.1