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Subject: Re: [PATCH 1/3] net: add a CMSG_USER_DATA macro
To:     Christoph Hellwig <hch@lst.de>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200511115913.1420836-1-hch@lst.de>
 <20200511115913.1420836-2-hch@lst.de>
From:   Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Message-ID: <f754c4ac-db7d-6688-5582-2a5f476b0f08@cogentembedded.com>
Date:   Tue, 12 May 2020 11:28:08 +0300
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Hello!

On 11.05.2020 14:59, Christoph Hellwig wrote:

> Add a variant of CMSG_DATA that operates on user pointer to avoid
> sparse warnings about casting to/from user pointers.  Also fix up
> CMSG_DATA to rely on the gcc extension that allows void pointer
> arithmetics to cut down on the amount of casts.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
[...]
> diff --git a/net/core/scm.c b/net/core/scm.c
> index dc6fed1f221c4..abfdc85a64c1b 100644
> --- a/net/core/scm.c
> +++ b/net/core/scm.c
[...]
> @@ -300,7 +300,7 @@ void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm)
>   	if (fdnum < fdmax)
>   		fdmax = fdnum;
>   
> -	for (i=0, cmfptr=(__force int __user *)CMSG_DATA(cm); i<fdmax;
> +	for (i=0, cmfptr =(int __user *)CMSG_USER_DATA(cm); i<fdmax;

    Perhaps it's time to add missing spaces consistently, not just one that 
you added?

>   	     i++, cmfptr++)
>   	{
>   		struct socket *sock;

MBR, Sergei