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Date: Fri, 12 Feb 2021 01:09:10 +0200
From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
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CC: Michal Hocko <mhocko@suse.com>, Mike Rapoport <rppt@linux.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>, Catalin Marinas <catalin.marinas@arm.com>, Christopher Lameter <cl@linux.com>, Dave Hansen <dave.hansen@linux.intel.com>, Elena Reshetova <elena.reshetova@intel.com>, "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>, James Bottomley <jejb@linux.ibm.com>, "Kirill A. Shutemov" <kirill@shutemov.name>, Matthew Wilcox <willy@infradead.org>, Mark Rutland <mark.rutland@arm.com>, Michael Kerrisk <mtk.manpages@gmail.com>, Palmer Dabbelt <palmer@dabbelt.com>, Paul Walmsley <paul.walmsley@sifive.com>, Peter Zijlstra <peterz@infradead.org>, Rick Edgecombe <rick.p.edgecombe@intel.com>, Roman Gushchin <guro@fb.com>, Shakeel Butt <shakeelb@google.com>, Shuah Khan <shuah@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Tycho Anders
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On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> On 11.02.21 12:27, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> 
> So let's talk about the main user-visible differences to other memfd files
> (especially, other purely virtual files like hugetlbfs). With secretmem:
> 
> - File content can only be read/written via memory mappings.
> - File content cannot be swapped out.
> 
> I think there are still valid ways to modify file content using syscalls:
> e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> fine.
 
These work perfectly with any file, so maybe we should have added
memfd_create as a flag to open(2) back then and now the secretmem file
descriptors?
 
> > > AFAIKS, we would need MFD_SECRET and disallow
> > > MFD_ALLOW_SEALING and MFD_HUGETLB.
> > 
> > So here we start to multiplex.
> 
> Yes. And as Michal said, maybe we can support combinations in the future.

Isn't there a general agreement that syscall multiplexing is not a good
thing?
memfd_create already has flags validation that does not look very nice.
Adding there only MFD_SECRET will make it a bit less nice, but when we'll
grow new functionality into secretmem that will become horrible.
 
-- 
Sincerely yours,
Mike.
_______________________________________________
Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org
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Date:   Fri, 12 Feb 2021 01:09:10 +0200
From:   Mike Rapoport <rppt@kernel.org>
To:     David Hildenbrand <david@redhat.com>
Cc:     Michal Hocko <mhocko@suse.com>, Mike Rapoport <rppt@linux.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Christopher Lameter <cl@linux.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Elena Reshetova <elena.reshetova@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        James Bottomley <jejb@linux.ibm.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Matthew Wilcox <willy@infradead.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Roman Gushchin <guro@fb.com>,
        Shakeel Butt <shakeelb@google.com>,
        Shuah Khan <shuah@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tycho Andersen <tycho@tycho.ws>, Will Deacon <will@kernel.org>,
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Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
Message-ID: <20210211230910.GL242749@kernel.org>
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On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> On 11.02.21 12:27, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> 
> So let's talk about the main user-visible differences to other memfd files
> (especially, other purely virtual files like hugetlbfs). With secretmem:
> 
> - File content can only be read/written via memory mappings.
> - File content cannot be swapped out.
> 
> I think there are still valid ways to modify file content using syscalls:
> e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> fine.
 
These work perfectly with any file, so maybe we should have added
memfd_create as a flag to open(2) back then and now the secretmem file
descriptors?
 
> > > AFAIKS, we would need MFD_SECRET and disallow
> > > MFD_ALLOW_SEALING and MFD_HUGETLB.
> > 
> > So here we start to multiplex.
> 
> Yes. And as Michal said, maybe we can support combinations in the future.

Isn't there a general agreement that syscall multiplexing is not a good
thing?
memfd_create already has flags validation that does not look very nice.
Adding there only MFD_SECRET will make it a bit less nice, but when we'll
grow new functionality into secretmem that will become horrible.
 
-- 
Sincerely yours,
Mike.

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 12 Feb 2021 01:09:10 +0200
From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
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 Tycho Andersen <tycho@tycho.ws>, linux-nvdimm@lists.01.org,
 Will Deacon <will@kernel.org>, x86@kernel.org,
 Matthew Wilcox <willy@infradead.org>, Mike Rapoport <rppt@linux.ibm.com>,
 Ingo Molnar <mingo@redhat.com>, Michael Kerrisk <mtk.manpages@gmail.com>,
 Palmer Dabbelt <palmerdabbelt@google.com>, Arnd Bergmann <arnd@arndb.de>,
 James Bottomley <jejb@linux.ibm.com>, Hagen Paul Pfeifer <hagen@jauu.net>,
 Borislav Petkov <bp@alien8.de>, Alexander Viro <viro@zeniv.linux.org.uk>,
 Andy Lutomirski <luto@kernel.org>, Paul Walmsley <paul.walmsley@sifive.com>,
 "Kirill A. Shutemov" <kirill@shutemov.name>,
 Dan Williams <dan.j.williams@intel.com>, linux-arm-kernel@lists.infradead.org,
 linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-riscv@lists.infradead.org, Palmer Dabbelt <palmer@dabbelt.com>,
 linux-fsdevel@vger.kernel.org, Shakeel Butt <shakeelb@google.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Rick Edgecombe <rick.p.edgecombe@intel.com>, Roman Gushchin <guro@fb.com>
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On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> On 11.02.21 12:27, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> 
> So let's talk about the main user-visible differences to other memfd files
> (especially, other purely virtual files like hugetlbfs). With secretmem:
> 
> - File content can only be read/written via memory mappings.
> - File content cannot be swapped out.
> 
> I think there are still valid ways to modify file content using syscalls:
> e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> fine.
 
These work perfectly with any file, so maybe we should have added
memfd_create as a flag to open(2) back then and now the secretmem file
descriptors?
 
> > > AFAIKS, we would need MFD_SECRET and disallow
> > > MFD_ALLOW_SEALING and MFD_HUGETLB.
> > 
> > So here we start to multiplex.
> 
> Yes. And as Michal said, maybe we can support combinations in the future.

Isn't there a general agreement that syscall multiplexing is not a good
thing?
memfd_create already has flags validation that does not look very nice.
Adding there only MFD_SECRET will make it a bit less nice, but when we'll
grow new functionality into secretmem that will become horrible.
 
-- 
Sincerely yours,
Mike.

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

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Date: Fri, 12 Feb 2021 01:09:10 +0200
From: Mike Rapoport <rppt@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v17 07/10] mm: introduce memfd_secret system call to
 create "secret" memory areas
Message-ID: <20210211230910.GL242749@kernel.org>
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Cc: Mark Rutland <mark.rutland@arm.com>, Michal Hocko <mhocko@suse.com>,
 Peter Zijlstra <peterz@infradead.org>,
 Catalin Marinas <catalin.marinas@arm.com>,
 Dave Hansen <dave.hansen@linux.intel.com>, linux-mm@kvack.org,
 linux-kselftest@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
 Christopher Lameter <cl@linux.com>, Shuah Khan <shuah@kernel.org>,
 Thomas Gleixner <tglx@linutronix.de>,
 Elena Reshetova <elena.reshetova@intel.com>, linux-arch@vger.kernel.org,
 Tycho Andersen <tycho@tycho.ws>, linux-nvdimm@lists.01.org,
 Will Deacon <will@kernel.org>, x86@kernel.org,
 Matthew Wilcox <willy@infradead.org>, Mike Rapoport <rppt@linux.ibm.com>,
 Ingo Molnar <mingo@redhat.com>, Michael Kerrisk <mtk.manpages@gmail.com>,
 Palmer Dabbelt <palmerdabbelt@google.com>, Arnd Bergmann <arnd@arndb.de>,
 James Bottomley <jejb@linux.ibm.com>, Hagen Paul Pfeifer <hagen@jauu.net>,
 Borislav Petkov <bp@alien8.de>, Alexander Viro <viro@zeniv.linux.org.uk>,
 Andy Lutomirski <luto@kernel.org>, Paul Walmsley <paul.walmsley@sifive.com>,
 "Kirill A. Shutemov" <kirill@shutemov.name>,
 Dan Williams <dan.j.williams@intel.com>, linux-arm-kernel@lists.infradead.org,
 linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-riscv@lists.infradead.org, Palmer Dabbelt <palmer@dabbelt.com>,
 linux-fsdevel@vger.kernel.org, Shakeel Butt <shakeelb@google.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Rick Edgecombe <rick.p.edgecombe@intel.com>, Roman Gushchin <guro@fb.com>
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On Thu, Feb 11, 2021 at 01:07:10PM +0100, David Hildenbrand wrote:
> On 11.02.21 12:27, Mike Rapoport wrote:
> > On Thu, Feb 11, 2021 at 10:01:32AM +0100, David Hildenbrand wrote:
> 
> So let's talk about the main user-visible differences to other memfd files
> (especially, other purely virtual files like hugetlbfs). With secretmem:
> 
> - File content can only be read/written via memory mappings.
> - File content cannot be swapped out.
> 
> I think there are still valid ways to modify file content using syscalls:
> e.g., fallocate(PUNCH_HOLE). Things like truncate also seems to work just
> fine.
 
These work perfectly with any file, so maybe we should have added
memfd_create as a flag to open(2) back then and now the secretmem file
descriptors?
 
> > > AFAIKS, we would need MFD_SECRET and disallow
> > > MFD_ALLOW_SEALING and MFD_HUGETLB.
> > 
> > So here we start to multiplex.
> 
> Yes. And as Michal said, maybe we can support combinations in the future.

Isn't there a general agreement that syscall multiplexing is not a good
thing?
memfd_create already has flags validation that does not look very nice.
Adding there only MFD_SECRET will make it a bit less nice, but when we'll
grow new functionality into secretmem that will become horrible.
 
-- 
Sincerely yours,
Mike.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel