From: Dan Williams <dan.j.williams@gmail.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: David Hildenbrand <david@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Alexey Dobriyan <adobriyan@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
James Bottomley <jejb@linux.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Linux API <linux-api@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
Mike Rapoport <rppt@linux.ibm.com>
Subject: Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings
Date: Thu, 31 Oct 2019 14:52:46 -0700 [thread overview]
Message-ID: <CAA9_cmdCmiu5wVs=Jo4c6VNw6N1raPTDXg4d9OuUj3w0+e5JHQ@mail.gmail.com> (raw)
In-Reply-To: <20191031191651.GA26165@rapoport-lnx>
On Thu, Oct 31, 2019 at 12:17 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> On Wed, Oct 30, 2019 at 09:19:33AM +0100, David Hildenbrand wrote:
> > On 30.10.19 09:15, Mike Rapoport wrote:
> > >On Tue, Oct 29, 2019 at 12:02:34PM +0100, David Hildenbrand wrote:
> > >>On 27.10.19 11:17, Mike Rapoport wrote:
> > >>>From: Mike Rapoport <rppt@linux.ibm.com>
> > >>>
> > >>>The mappings created with MAP_EXCLUSIVE are visible only in the context of
> > >>>the owning process and can be used by applications to store secret
> > >>>information that will not be visible not only to other processes but to the
> > >>>kernel as well.
> > >>>
> > >>>The pages in these mappings are removed from the kernel direct map and
> > >>>marked with PG_user_exclusive flag. When the exclusive area is unmapped,
> > >>>the pages are mapped back into the direct map.
> > >>>
> > >>
> > >>Just a thought, the kernel is still able to indirectly read the contents of
> > >>these pages by doing a kdump from kexec environment, right?
> > >
> > >Right.
> > >
> > >>Also, I wonder
> > >>what would happen if you map such pages via /dev/mem into another user space
> > >>application and e.g., use them along with kvm [1].
> > >
> > >Do you mean that one application creates MAP_EXCLUSIVE and another
> > >applications accesses the same physical pages via /dev/mem?
> >
> > Exactly.
> >
> > >
> > >With /dev/mem all physical memory is visible...
> >
> > Okay, so the statement "information that will not be visible not only to
> > other processes but to the kernel as well" is not correct. There are easy
> > ways to access that information if you really want to (might require root
> > permissions, though).
>
> Right, but /dev/mem is an easy way to extract any information in any
> environment if one has root permissions...
>
I don't understand this concern with /dev/mem. Just add these pages to
the growing list of the things /dev/mem is not allowed to touch.
next prev parent reply other threads:[~2019-10-31 21:53 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-27 10:17 [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Mike Rapoport
2019-10-27 10:17 ` Mike Rapoport
2019-10-28 12:31 ` Kirill A. Shutemov
2019-10-28 13:00 ` Mike Rapoport
2019-10-28 13:16 ` Kirill A. Shutemov
2019-10-28 13:55 ` Peter Zijlstra
2019-10-28 19:59 ` Edgecombe, Rick P
2019-10-28 21:00 ` Peter Zijlstra
2019-10-29 17:27 ` Edgecombe, Rick P
2019-10-30 10:04 ` Peter Zijlstra
2019-10-30 15:35 ` Alexei Starovoitov
2019-10-30 18:39 ` Peter Zijlstra
2019-10-30 18:52 ` Alexei Starovoitov
2019-10-30 17:48 ` Edgecombe, Rick P
2019-10-30 17:58 ` Dave Hansen
2019-10-30 18:01 ` Dave Hansen
2019-10-29 5:43 ` Dan Williams
2019-10-29 6:43 ` Kirill A. Shutemov
2019-10-29 8:56 ` Peter Zijlstra
2019-10-29 11:00 ` Kirill A. Shutemov
2019-10-29 12:39 ` AMD TLB errata, (Was: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings) Peter Zijlstra
2019-11-15 14:12 ` Tom Lendacky
2019-11-15 14:31 ` Peter Zijlstra
2019-10-29 19:43 ` [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Dan Williams
2019-10-29 20:07 ` Dave Hansen
2019-10-29 7:08 ` Christopher Lameter
2019-10-29 8:55 ` Mike Rapoport
2019-10-29 10:12 ` Christopher Lameter
2019-10-30 7:11 ` Mike Rapoport
2019-10-30 12:09 ` Christopher Lameter
2019-10-28 14:55 ` David Hildenbrand
2019-10-28 17:12 ` Dave Hansen
2019-10-28 17:32 ` Sean Christopherson
2019-10-28 18:08 ` Matthew Wilcox
2019-10-29 9:28 ` Mike Rapoport
2019-10-29 9:19 ` Mike Rapoport
2019-10-28 18:02 ` Andy Lutomirski
2019-10-29 11:02 ` David Hildenbrand
2019-10-30 8:15 ` Mike Rapoport
2019-10-30 8:19 ` David Hildenbrand
2019-10-31 19:16 ` Mike Rapoport
2019-10-31 21:52 ` Dan Williams [this message]
2019-10-27 10:30 ` Florian Weimer
2019-10-27 11:00 ` Mike Rapoport
2019-10-28 20:23 ` Florian Weimer
2019-10-29 9:01 ` Mike Rapoport
2019-10-28 20:44 ` Andy Lutomirski
2019-10-29 9:32 ` Mike Rapoport
2019-10-29 17:00 ` Andy Lutomirski
2019-10-30 8:40 ` Mike Rapoport
2019-10-30 21:28 ` Andy Lutomirski
2019-10-31 7:21 ` Mike Rapoport
2019-12-05 15:34 ` Mike Rapoport
2019-12-08 14:10 ` [PATCH] mm: extend memfd with ability to create secret memory kbuild test robot
2019-10-29 11:25 ` [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings Reshetova, Elena
2019-10-29 15:13 ` Tycho Andersen
2019-10-29 17:03 ` Andy Lutomirski
2019-10-29 17:37 ` Alan Cox
2019-10-29 17:43 ` James Bottomley
2019-10-29 18:10 ` Andy Lutomirski
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