Re: [PATCH] IB/mlx4: prevent undefined shift in set_user_sq_size()

[Jason Gunthorpe]

On Sat, Jun 08, 2019 at 12:22:31PM +0300, Dan Carpenter wrote:
> The ucmd->log_sq_bb_count is a u8 that comes from the user.  If it's
> larger than the number of bits in an int then that's undefined behavior.
> It turns out this doesn't really cause an issue at runtime but it's
> still nice to clean it up.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
>  drivers/infiniband/hw/mlx4/qp.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
> index 5221c0794d1d..9f6eb23e8044 100644
> --- a/drivers/infiniband/hw/mlx4/qp.c
> +++ b/drivers/infiniband/hw/mlx4/qp.c
> @@ -439,7 +439,8 @@ static int set_user_sq_size(struct mlx4_ib_dev *dev,
>  			    struct mlx4_ib_create_qp *ucmd)
>  {
>  	/* Sanity check SQ size before proceeding */
> -	if ((1 << ucmd->log_sq_bb_count) > dev->dev->caps.max_wqes	 ||
> +	if (ucmd->log_sq_bb_count > 31					 ||
> +	    (1 << ucmd->log_sq_bb_count) > dev->dev->caps.max_wqes	 ||

Surely this should use check_shl_overflow() ?

Jason