linux-kernel - Re: [PATCH v20 4/7] mm: introduce memfd_secret system call to create "secret" memory areas

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Date:   Tue, 18 May 2021 17:44:22 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     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>,
        Dan Williams <dan.j.williams@...el.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>,
        Hagen Paul Pfeifer <hagen@...u.net>,
        Ingo Molnar <mingo@...hat.com>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Matthew Garrett <mjg59@...f.ucam.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>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        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>,
        Yury Norov <yury.norov@...il.com>, linux-api@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org
Subject: Re: [PATCH v20 4/7] mm: introduce memfd_secret system call to
 create "secret" memory areas

On Tue, 18 May 2021 10:20:31 +0300 Mike Rapoport <rppt@...nel.org> wrote:

> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> Introduce "memfd_secret" system call with the ability to create memory
> areas visible only in the context of the owning process and not mapped not
> only to other processes but in the kernel page tables as well.
> 
> ...
>
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -901,4 +901,9 @@ config KMAP_LOCAL
>  # struct io_mapping based helper.  Selected by drivers that need them
>  config IO_MAPPING
>  	bool
> +
> +config SECRETMEM
> +	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
> +	select STRICT_DEVMEM
> +
>  endmenu

WARNING: unmet direct dependencies detected for STRICT_DEVMEM
  Depends on [n]: MMU [=y] && DEVMEM [=n] && (ARCH_HAS_DEVMEM_IS_ALLOWED [=y] || GENERIC_LIB_DEVMEM_IS_ALLOWED [=n])
  Selected by [y]:
  - SECRETMEM [=y]

so I went back to the v19 version, with

--- a/mm/Kconfig~mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas-fix
+++ a/mm/Kconfig
@@ -907,6 +907,5 @@ config IO_MAPPING
 
 config SECRETMEM
 	def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
-	select STRICT_DEVMEM
 
 endmenu
_