Re: [PATCH v2 56/63] RDMA/mlx5: Use struct_group() to zero struct mlx5_ib_mr

Jason Gunthorpe
2021-08-19T12:27:23Z

On Tue, Aug 17, 2021 at 11:05:26PM -0700, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
>
> Add struct_group() to mark region of struct mlx5_ib_mr that should be
> initialized to zero.
>
> Cc: Leon Romanovsky <leon@kernel.org>
> Cc: Doug Ledford <dledford@redhat.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: linux-rdma@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> drivers/infiniband/hw/mlx5/mlx5_ib.h | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> index bf20a388eabe..f63bf204a7a1 100644
> --- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
> +++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> @@ -644,6 +644,7 @@ struct mlx5_ib_mr {
> struct ib_umem *umem;
>
> /* This is zero'd when the MR is allocated */
> + struct_group(cleared,
> union {
> /* Used only while the MR is in the cache */
> struct {
> @@ -691,12 +692,13 @@ struct mlx5_ib_mr {
> bool is_odp_implicit;
> };
> };
> + );
> };
>
> /* Zero the fields in the mr that are variant depending on usage */
> static inline void mlx5_clear_mr(struct mlx5_ib_mr *mr)
> {
> - memset(mr->out, 0, sizeof(*mr) - offsetof(struct mlx5_ib_mr, out));
> + memset(&mr->cleared, 0, sizeof(mr->cleared));
> }

Why not use the memset_after(mr->umem) here?

Jason