netdev - Re: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting

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Date:   Sun, 14 Jan 2018 15:07:19 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Christopher Lameter <cl@...ux.com>
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: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting

On Wed, Jan 10, 2018 at 12:28:23PM -0600, Christopher Lameter wrote:
> On Tue, 9 Jan 2018, Kees Cook wrote:
> > +struct kmem_cache *kmem_cache_create_usercopy(const char *name,
> > +			size_t size, size_t align, slab_flags_t flags,
> > +			size_t useroffset, size_t usersize,
> > +			void (*ctor)(void *));
> 
> Hmmm... At some point we should switch kmem_cache_create to pass a struct
> containing all the parameters. Otherwise the API will blow up with
> additional functions.

Obviously I agree with you.  I'm inclined to not let that delay Kees'
patches; we can fix the few places that use this API later.  At this
point, my proposal for the ultimate form would be:

struct kmem_cache_attr {
	const char name[32];
	void (*ctor)(void *);
	unsigned int useroffset;
	unsigned int user_size; 
};

kmem_create_cache_attr(const struct kmem_cache_attr *attr, unsigned int size,
			unsigned int align, slab_flags_t flags)

(my rationale is that everything in attr should be const, but size, align
and flags all get modified by the slab code).