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

[Christopher Lameter <cl@linux.com>]

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;
	...
}