# \[PATCH 3/6\] struct page: add field for vm\_struct

- From: Christopher Lameter \<hidden\>
- Date: 2018-02-02 18:43:25 
- List: linux-security-module
- Page: https://ratatoskr.run/linux-security-module/2018/02/5199662
- Thread: https://ratatoskr.run/linux-security-module/2018/01/5183216/t.md

```text
On Thu, 1 Feb 2018, Igor Stoppa wrote:

> > Would it not be better to use compound page allocations here?
> > page_head(whatever) gets you the head page where you can store all sorts
> > of information about the chunk of memory.
>
> Can you please point me to this function/macro? I don't seem to be able
> to find it, at least not in 4.15

Ok its compound_head(). See also the use in the SLAB and SLUB allocator.

> During hardened user copy permission check, I need to confirm if the
> memory range that would be exposed to userspace is a legitimate
> sub-range of a pmalloc allocation.

If you save the size in the head page struct then you could do that pretty
fast.

> I cannot comment on your proposal because I do not know where to find
> the reference you made, or maybe I do not understand what you mean :-(

compund pages are higher order pages that are handled as a single page by
the VM. See https://lwn.net/Articles/619514/
--
To unsubscribe from this list: send the line "unsubscribe linux-security-module" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
```