netdev - Re: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting)

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Date:   Wed, 17 Jan 2018 08:46:41 -0600 (CST)
From:   Christopher Lameter <cl@...ux.com>
To:     Matthew Wilcox <willy@...radead.org>
cc:     Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
        David Windsor <dave@...lcore.net>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-xfs@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        Laura Abbott <labbott@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Jan Kara <jack@...e.cz>,
        Luis de Bethencourt <luisbg@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Rik van Riel <riel@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        linux-fsdevel@...r.kernel.org, linux-arch@...r.kernel.org,
        netdev@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for
 usercopy whitelisting)

On Tue, 16 Jan 2018, Matthew Wilcox wrote:

> On Tue, Jan 16, 2018 at 12:17:01PM -0600, Christopher Lameter wrote:
> > Draft patch of how the data structs could change. kmem_cache_attr is read
> > only.
>
> Looks good.  Although I would add Kees' user feature:

Sure I tried to do this quickly so that the basic struct changes are
visible.

> And I'd start with
> +struct kmem_cache *kmem_cache_create_attr(const kmem_cache_attr *);
>
> leaving the old kmem_cache_create to kmalloc a kmem_cache_attr and
> initialise it.

Well at some point we should convert the callers by putting the
definitions into const kmem_cache_attr initializations. That way
the callbacks function pointers are safe.

> Can we also do something like this?
>
> -#define KMEM_CACHE(__struct, __flags) kmem_cache_create(#__struct,\
> -		sizeof(struct __struct), __alignof__(struct __struct),\
> -		(__flags), NULL)
> +#define KMEM_CACHE(__struct, __flags) ({				\
> +	const struct kmem_cache_attr kca ## __stringify(__struct) = {	\
> +		.name = #__struct,					\
> +		.size = sizeof(struct __struct),			\
> +		.align = __alignof__(struct __struct),			\
> +		.flags = (__flags),					\
> +	};								\
> +	kmem_cache_create_attr(&kca ## __stringify(__struct));		\
> +})
>
> That way we won't need to convert any of those users.

Yep thats what I was planning.