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Date: Mon, 31 Jan 2022 19:27:35 +0000 From: Matthew Wilcox <willy@...radead.org> To: David Hildenbrand <david@...hat.com> Cc: Kees Cook <keescook@...omium.org>, linux-mm@...ck.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH 4/4] usercopy: Remove HARDENED_USERCOPY_PAGESPAN On Mon, Jan 31, 2022 at 03:27:02PM +0100, David Hildenbrand wrote: > On 11.01.22 00:15, Matthew Wilcox (Oracle) wrote: > > There isn't enough information to make this a useful check any more; > > the useful parts of it were moved in earlier patches, so remove this > > set of checks now. > > > > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org> > > > Very nice cleanup IMHO > > Reviewed-by: David Hildenbrand <david@...hat.com> Thanks. I'm thinking about adding another check. If the order-0 page has a non-NULL ->mapping, I believe that is enough to determine that it's a page cache / KSM / Anon page, and as such is guaranteed to actually be order-0 (and not part of a postive-order allocation without __GFP_COMP set). But that would require a bit more auditing, or just throwing it in and seeing what breaks *whistles*.
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