linux-kernel - Re: [PATCH v17 08/10] PM: hibernate: disable when there are active secretmem users

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Date:   Mon, 22 Feb 2021 11:17:46 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Matthew Garrett <mjg59@...f.ucam.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christopher Lameter <cl@...ux.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Michal Hocko <mhocko@...e.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        Linux API <linux-api@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        linux-riscv@...ts.infradead.org, X86 ML <x86@...nel.org>,
        Hagen Paul Pfeifer <hagen@...u.net>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH v17 08/10] PM: hibernate: disable when there are active
 secretmem users

On Mon, Feb 22, 2021 at 2:24 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> On Mon, Feb 22, 2021 at 07:34:52AM +0000, Matthew Garrett wrote:
> > On Mon, Feb 08, 2021 at 10:49:18AM +0200, Mike Rapoport wrote:
> >
> > > It is unsafe to allow saving of secretmem areas to the hibernation
> > > snapshot as they would be visible after the resume and this essentially
> > > will defeat the purpose of secret memory mappings.
> >
> > Sorry for being a bit late to this - from the point of view of running
> > processes (and even the kernel once resume is complete), hibernation is
> > effectively equivalent to suspend to RAM. Why do they need to be handled
> > differently here?
>
> Hibernation leaves a copy of the data on the disk which we want to prevent.

Why not document that users should use data at rest protection
mechanisms for their hibernation device? Just because secretmem can't
assert its disclosure guarantee does not mean the hibernation device
is untrustworthy.