linux-kernel - Re: [PATCH][next] RDMA/mlx4: Copy union directly

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Message-ID: <202308151642.794EB1B64@keescook>
Date:   Tue, 15 Aug 2023 16:42:45 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Yishai Hadas <yishaih@...dia.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][next] RDMA/mlx4: Copy union directly

On Tue, Aug 15, 2023 at 02:39:53PM -0600, Gustavo A. R. Silva wrote:
> Copy union directly instead of using memcpy().
> 
> Note that in this case, a direct assignment is more readable and
> consistent with the subsequent assignments.
> 
> This addresses the following -Wstringop-overflow warning seen in s390
> with defconfig:
> drivers/infiniband/hw/mlx4/main.c:296:33: warning: writing 16 bytes into a region of size 0 [-Wstringop-overflow=]
>   296 |                                 memcpy(&port_gid_table->gids[free].gid,
>       |                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   297 |                                        &attr->gid, sizeof(attr->gid));
>       |                                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hm, why did it think the union had a size of 0?

Regardless, it's a nice fix:

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook