Date: Sun, 14 Jan 2018 15:07:19 -0800
From: Matthew Wilcox <willy@infradead.org>
To: Christopher Lameter <cl@linux.com>
Cc: Kees Cook <keescook@chromium.org>, linux-kernel@vger.kernel.org,
        David Windsor <dave@nullcore.net>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-xfs@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        "David S. Miller" <davem@davemloft.net>,
        Laura Abbott <labbott@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        Christoffer Dall <christoffer.dall@linaro.org>,
        Dave Kleikamp <dave.kleikamp@oracle.com>,
        Jan Kara <jack@suse.cz>,
        Luis de Bethencourt <luisbg@kernel.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Rik van Riel <riel@redhat.com>,
        Matthew Garrett <mjg59@google.com>,
        linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org,
        netdev@vger.kernel.org, kernel-hardening@lists.openwall.com
Subject: Re: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting
Message-ID: <20180114230719.GB32027@bombadil.infradead.org>
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 <alpine.DEB.2.20.1801101219390.7926@nuc-kabylake>
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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).