linux-kernel - Re: [PATCH] RDMA/ucma: Use struct

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Message-ID: <20190605042938.GL5261@mtr-leonro.mtl.com>
Date:   Wed, 5 Jun 2019 07:29:38 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Doug Ledford <dledford@...hat.com>, Jason Gunthorpe <jgg@...pe.ca>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RDMA/ucma: Use struct_size() helper

On Tue, Jun 04, 2019 at 10:42:22AM -0500, Gustavo A. R. Silva wrote:
> Make use of the struct_size() helper instead of an open-coded version
> in order to avoid any potential type mistakes, in particular in the
> context in which this code is being used.

What does "in particular in the context in which this code is being
used" mean?

>
> So, replace the following form:
>
> sizeof(*resp) + (i * sizeof(struct ib_path_rec_data))
>
> with:
>
> struct_size(resp, path_data, i)

It is already written inside commit itself.

>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/infiniband/core/ucma.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
> index 140a338a135f..cbe460076611 100644
> --- a/drivers/infiniband/core/ucma.c
> +++ b/drivers/infiniband/core/ucma.c
> @@ -951,8 +951,7 @@ static ssize_t ucma_query_path(struct ucma_context *ctx,
>  		}
>  	}
>
> -	if (copy_to_user(response, resp,
> -			 sizeof(*resp) + (i * sizeof(struct ib_path_rec_data))))
> +	if (copy_to_user(response, resp, struct_size(resp, path_data, i)))
>  		ret = -EFAULT;
>
>  	kfree(resp);
> --
> 2.21.0
>