[PATCH v2] nvme: Fix handling of large MDTS values

[Keith Busch]

On Wed, Mar 31, 2021 at 08:59:52PM -0700, Bart Van Assche wrote:
> Instead of triggering an integer overflow and undefined behavior if MDTS is
> large, set max_hw_sectors to UINT_MAX.
>
> Signed-off-by: Bart Van Assche <bvanassche at acm.org>
> ---
> 
> Changes compared to v1: removed a dev_err() call.
> 
>  drivers/nvme/host/core.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 40215a0246e4..25bc28e8845f 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3123,10 +3123,11 @@ static int nvme_init_identify(struct nvme_ctrl *ctrl)
>  
>  	atomic_set(&ctrl->abort_limit, id->acl + 1);
>  	ctrl->vwc = id->vwc;
> -	if (id->mdts)
> -		max_hw_sectors = 1 << (id->mdts + page_shift - 9);
> -	else
> +	max_hw_sectors = UINT_MAX;
> +	if (id->mdts && check_shl_overflow(1U, id->mdts + page_shift - 9,
> +					   &max_hw_sectors)) {
>  		max_hw_sectors = UINT_MAX;
> +	}

The condition can be rearranged so that max_hw_sectors is set to
UINT_MAX just once:

	if (!id->mdts || check_shl_overflow(1U, id->mdts + page_shift - 9,
					    &max_hw_sectors)) {
  		max_hw_sectors = UINT_MAX;
	}

>  	ctrl->max_hw_sectors =
>  		min_not_zero(ctrl->max_hw_sectors, max_hw_sectors);
>