linux-hardening - Re: [PATCH 19/64] ip: Use struct

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Message-ID: <202107281358.8E12638@keescook>
Date:   Wed, 28 Jul 2021 14:01:24 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-hardening@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Keith Packard <keithpac@...zon.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH 19/64] ip: Use struct_group() for memcpy() regions

On Wed, Jul 28, 2021 at 07:55:53AM +0200, Greg Kroah-Hartman wrote:
> >  struct ethhdr {
> > -	unsigned char	h_dest[ETH_ALEN];	/* destination eth addr	*/
> > -	unsigned char	h_source[ETH_ALEN];	/* source ether addr	*/
> > +	union {
> > +		struct {
> > +			unsigned char h_dest[ETH_ALEN];	  /* destination eth addr */
> > +			unsigned char h_source[ETH_ALEN]; /* source ether addr	  */
> > +		};
> > +		struct {
> > +			unsigned char h_dest[ETH_ALEN];	  /* destination eth addr */
> > +			unsigned char h_source[ETH_ALEN]; /* source ether addr	  */
> > +		} addrs;
> 
> A union of the same fields in the same structure in the same way?
> 
> Ah, because struct_group() can not be used here?  Still feels odd to see
> in a userspace-visible header.

Yeah, there is some inconsistency here. I will clean this up for v2.

Is there a place we can put kernel-specific macros for use in UAPI
headers? (I need to figure out where things like __kernel_size_t get
defined...)

-- 
Kees Cook