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

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Message-ID: <alpine.DEB.2.20.1801160913260.3908@nuc-kabylake>
Date:   Tue, 16 Jan 2018 09:21:30 -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: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for usercopy
 whitelisting)

On Sun, 14 Jan 2018, Matthew Wilcox wrote:

> > 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:

Right. Thats why I said "at some point"....

>
> struct kmem_cache_attr {
> 	const char name[32];

Want to avoid the string reference mess that occurred in the past?
Is that really necessary? But it would limit the size of the name.

> 	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).

Thought about putting all the parameters into the kmem_cache_attr struct.

So

struct kmem_cache_attr {
	char *name;
	size_t size;
	size_t align;
	slab_flags_t flags;
	unsigned int useroffset;
	unsinged int usersize;
	void (*ctor)(void *);
	kmem_isolate_func *isolate;
	kmem_migrate_func *migrate;
	...
}