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

From: Matthew Wilcox
Date: Sun Jan 14 2018 - 18:07:44 EST


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).