linux-kernel - Re: [PATCH] IB/mlx4: Avoid field-overflowing memcpy()

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Message-ID: <YMr4ypsh7D3q1R5+@unreal>
Date:   Thu, 17 Jun 2021 10:24:58 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Kees Cook <keescook@...omium.org>,
        Jack Morgenstein <jackm@...dia.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, Yishai Hadas <yishaih@...dia.com>,
        Doug Ledford <dledford@...hat.com>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] IB/mlx4: Avoid field-overflowing memcpy()

On Wed, Jun 16, 2021 at 01:37:44PM -0700, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memcpy(), memmove(), and memset(), avoid
> intentionally writing across neighboring array fields.
> 
> Use the ether_addr_copy() helper instead, as already done for smac.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/infiniband/hw/mlx4/qp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
> index 2ae22bf50016..4a2ef7daaded 100644
> --- a/drivers/infiniband/hw/mlx4/qp.c
> +++ b/drivers/infiniband/hw/mlx4/qp.c
> @@ -3144,7 +3144,7 @@ static int build_mlx_header(struct mlx4_ib_qp *qp, const struct ib_ud_wr *wr,
>  		mlx->sched_prio = cpu_to_be16(pcp);
>  
>  		ether_addr_copy(sqp->ud_header.eth.smac_h, ah->av.eth.s_mac);
> -		memcpy(sqp->ud_header.eth.dmac_h, ah->av.eth.mac, 6);
> +		ether_addr_copy(sqp->ud_header.eth.dmac_h, ah->av.eth.mac);
>  		memcpy(&ctrl->srcrb_flags16[0], ah->av.eth.mac, 2);
>  		memcpy(&ctrl->imm, ah->av.eth.mac + 2, 4);

I don't understand the last three lines. We are copying 6 bytes to
ah->av.eth.mac and immediately after that overwriting them.

Jack, 

Do you remember what you wanted to achieve in commit
6ee51a4e866b ("mlx4: Adjust QP1 multiplexing for RoCE/SRIOV")

Thanks

>  
> -- 
> 2.25.1
>