linux-kernel - Re: [PATCH v2] RDMA/mlx5: Use memset_after() to zero struct mlx5_ib

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Date:   Mon, 13 Dec 2021 18:39:09 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-hardening@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: Re: [PATCH v2] RDMA/mlx5: Use memset_after() to zero struct
 mlx5_ib_mr

On Tue, Dec 07, 2021 at 01:20:22PM -0800, 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.
> 
> Use memset_after() to zero the end of struct mlx5_ib_mr that should
> be initialized.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks
--
Gustavo

> ---
> v2: rebased, umem moved into the union and is expected to be wiped
>     https://lore.kernel.org/lkml/20211207194525.GL6385@nvidia.com
> ---
>  drivers/infiniband/hw/mlx5/mlx5_ib.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> index 4a7a56ed740b..ded10719b643 100644
> --- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
> +++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> @@ -664,8 +664,8 @@ struct mlx5_ib_mr {
>  
>  	/* User MR data */
>  	struct mlx5_cache_ent *cache_ent;
> +	/* Everything after cache_ent is zero'd when MR allocated */
>  
> -	/* This is zero'd when the MR is allocated */
>  	union {
>  		/* Used only while the MR is in the cache */
>  		struct {
> @@ -718,7 +718,7 @@ struct mlx5_ib_mr {
>  /* 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_after(mr, 0, cache_ent);
>  }
>  
>  static inline bool is_odp_mr(struct mlx5_ib_mr *mr)
> -- 
> 2.30.2
> 
> 
> 
>