linux-kernel - Re: [PATCH 06/19] mm/pagewalk: Check pfnmap early for folio_walk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZsNS86OE_sGzwZW2@google.com>
Date: Mon, 19 Aug 2024 07:19:07 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: David Hildenbrand <david@...hat.com>, Peter Xu <peterx@...hat.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Oscar Salvador <osalvador@...e.de>, 
	Axel Rasmussen <axelrasmussen@...gle.com>, linux-arm-kernel@...ts.infradead.org, 
	x86@...nel.org, Will Deacon <will@...nel.org>, Gavin Shan <gshan@...hat.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, Zi Yan <ziy@...dia.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Catalin Marinas <catalin.marinas@....com>, 
	Ingo Molnar <mingo@...hat.com>, Alistair Popple <apopple@...dia.com>, Borislav Petkov <bp@...en8.de>, 
	Thomas Gleixner <tglx@...utronix.de>, kvm@...r.kernel.org, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Alex Williamson <alex.williamson@...hat.com>, 
	Yan Zhao <yan.y.zhao@...el.com>
Subject: Re: [PATCH 06/19] mm/pagewalk: Check pfnmap early for folio_walk_start()

On Mon, Aug 19, 2024, Jason Gunthorpe wrote:
> On Fri, Aug 16, 2024 at 07:56:30PM +0200, David Hildenbrand wrote:
> 
> > I think KVM does something nasty: if it something with a "struct page", and
> > it's not PageReserved, it would take a reference (if I get
> > kvm_pfn_to_refcounted_page()) independent if it's a "normal" or "not normal"
> > page -- it essentially ignores the vm_normal_page() information in the page
> > tables ...
> 
> Oh that's nasty. Nothing should be upgrading the output of the follow
> functions to refcounted. That's what GUP is for.
> 
> And PFNMAP pages, even if they have struct pages for some reason,
> should *NEVER* be refcounted because they are in a PFNMAP VMA. That is
> completely against the whole point :\ If they could be safely
> refcounted then it would be a MIXEDMAP.

Yeah yeah, I'm working on it.

https://lore.kernel.org/all/20240726235234.228822-1-seanjc@google.com