linux-hardening - Re: [PATCH] IB/rdmavt: Fix target union member for rvt_post_one

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Date:   Tue, 21 Feb 2023 08:00:12 -0500
From:   Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Zhang Yi <yizhan@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] IB/rdmavt: Fix target union member for rvt_post_one_wr()

On 2/18/23 1:57 PM, Kees Cook wrote:
> The "cplen" result used by the memcpy() into struct rvt_swqe "wqe" may
> be sized to 80 for struct rvt_ud_wr (which is member "ud_wr", not "wr"
> which is only 40 bytes in size). Change the destination union member so
> the compiler can use the correct bounds check.
> 
> struct rvt_swqe {
>         union {
>                 struct ib_send_wr wr;   /* don't use wr.sg_list */
>                 struct rvt_ud_wr ud_wr;
> 		...
> 	};
> 	...
> };
> 
> Silences false positive memcpy() run-time warning:
> 
>   memcpy: detected field-spanning write (size 80) of single field "&wqe->wr" at drivers/infiniband/sw/rdmavt/qp.c:2043 (size 40)
> 
> Reported-by: Zhang Yi <yizhan@...hat.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216561
> Cc: Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: linux-rdma@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  drivers/infiniband/sw/rdmavt/qp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
> index 3acab569fbb9..3f707e1fa517 100644
> --- a/drivers/infiniband/sw/rdmavt/qp.c
> +++ b/drivers/infiniband/sw/rdmavt/qp.c
> @@ -2040,7 +2040,7 @@ static int rvt_post_one_wr(struct rvt_qp *qp,
>  	wqe = rvt_get_swqe_ptr(qp, qp->s_head);
>  
>  	/* cplen has length from above */
> -	memcpy(&wqe->wr, wr, cplen);
> +	memcpy(&wqe->ud_wr, wr, cplen);
>  
>  	wqe->length = 0;
>  	j = 0;

Thanks for the patch. We've been debating this issue internally since last week.
The problem I have is this makes it look like everything is a "UD" req when it
could be a different QP type. Maybe we just need a comment explaining.

-Denny