Date: Tue, 16 Jan 2018 13:03:13 -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: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for
 usercopy whitelisting)
Message-ID: <20180116210313.GA7791@bombadil.infradead.org>
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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:

struct kmem_cache_attr {
	char name[16];
	unsigned int size;
	unsigned int align;
+	unsigned int useroffset;
+	unsigned int usersize;
	slab_flags_t flags;
	kmem_cache_ctor ctor;
}

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.

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.