From patchwork Thu Sep 24 13:28:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Rapoport X-Patchwork-Id: 11797269 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DF5F792C for ; Thu, 24 Sep 2020 13:29:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCD2A23772 for ; Thu, 24 Sep 2020 13:29:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600954164; bh=oMnQkmIke2EbG8i1xZ6PRGZiyu34wgJzYF+0mpDqH74=; h=From:To:Cc:Subject:Date:List-ID:From; b=bTPy+DBCh5ywE1PMSbboW3ve3Hd4ZvCBfEPDGwlIXGb0Zb2MKsorbtOT45v9FZtS5 4jGGtnktllQ3g1tRfQraNs0abkwAPvFKfm/KpFg1Toi77X/me5Sp7FD9eeY6BgYE36 0EWkuh0MGyo9xhTihGik14Q4CeKaAch5OpuU/U+I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727962AbgIXN3V (ORCPT ); Thu, 24 Sep 2020 09:29:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:49414 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727809AbgIXN3U (ORCPT ); Thu, 24 Sep 2020 09:29:20 -0400 Received: from aquarius.haifa.ibm.com (nesher1.haifa.il.ibm.com [195.110.40.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E1A6D2076D; Thu, 24 Sep 2020 13:29:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600954159; bh=oMnQkmIke2EbG8i1xZ6PRGZiyu34wgJzYF+0mpDqH74=; h=From:To:Cc:Subject:Date:From; b=XiiU0oQ0I8gxLMSVN9RQEEmvUcp2Am+QmdMIuSNpjeQAdhy185feEYovF6YTIr5Vz XME0HCGcvBadbdH3QboRSOdukRZWPL6DBjqVqMhMVhRbbRIWYSC0Vz9dbDs9577fXw x7MPVWPytFrdo94kQiywkxhotxdf1F9r1kNH1oBc= From: Mike Rapoport To: Andrew Morton Cc: Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , David Hildenbrand , Elena Reshetova , "H. Peter Anvin" , Idan Yaniv , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Mark Rutland , Mike Rapoport , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Thomas Gleixner , Shuah Khan , Tycho Andersen , Will Deacon , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org Subject: [PATCH v6 0/6] mm: introduce memfd_secret system call to create "secret" memory areas Date: Thu, 24 Sep 2020 16:28:58 +0300 Message-Id: <20200924132904.1391-1-rppt@kernel.org> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org From: Mike Rapoport Hi, This is an implementation of "secret" mappings backed by a file descriptor. I've dropped the boot time reservation patch for now as it is not strictly required for the basic usage and can be easily added later either with or without CMA. v6 changes: * Silence the warning about missing syscall, thanks to Qian Cai * Replace spaces with tabs in Kconfig additions, per Randy * Add a selftest. v5 changes: * rebase on v5.9-rc5 * drop boot time memory reservation patch v4 changes: * rebase on v5.9-rc1 * Do not redefine PMD_PAGE_ORDER in fs/dax.c, thanks Kirill * Make secret mappings exclusive by default and only require flags to memfd_secret() system call for uncached mappings, thanks again Kirill :) v3 changes: * Squash kernel-parameters.txt update into the commit that added the command line option. * Make uncached mode explicitly selectable by architectures. For now enable it only on x86. v2 changes: * Follow Michael's suggestion and name the new system call 'memfd_secret' * Add kernel-parameters documentation about the boot option * Fix i386-tinyconfig regression reported by the kbuild bot. CONFIG_SECRETMEM now depends on !EMBEDDED to disable it on small systems from one side and still make it available unconditionally on architectures that support SET_DIRECT_MAP. The file descriptor backing secret memory mappings is created using a dedicated memfd_secret system call The desired protection mode for the memory is configured using flags parameter of the system call. The mmap() of the file descriptor created with memfd_secret() will create a "secret" memory mapping. The pages in that mapping will be marked as not present in the direct map and will have desired protection bits set in the user page table. For instance, current implementation allows uncached mappings. Although normally Linux userspace mappings are protected from other users, such secret mappings are useful for environments where a hostile tenant is trying to trick the kernel into giving them access to other tenants mappings. Additionally, the secret mappings may be used as a mean to protect guest memory in a virtual machine host. For demonstration of secret memory usage we've created a userspace library [1] that does two things: the first is act as a preloader for openssl to redirect all the OPENSSL_malloc calls to secret memory meaning any secret keys get automatically protected this way and the other thing it does is expose the API to the user who needs it. We anticipate that a lot of the use cases would be like the openssl one: many toolkits that deal with secret keys already have special handling for the memory to try to give them greater protection, so this would simply be pluggable into the toolkits without any need for user application modification. I've hesitated whether to continue to use new flags to memfd_create() or to add a new system call and I've decided to use a new system call after I've started to look into man pages update. There would have been two completely independent descriptions and I think it would have been very confusing. Hiding secret memory mappings behind an anonymous file allows (ab)use of the page cache for tracking pages allocated for the "secret" mappings as well as using address_space_operations for e.g. page migration callbacks. The anonymous file may be also used implicitly, like hugetlb files, to implement mmap(MAP_SECRET) and use the secret memory areas with "native" mm ABIs in the future. As the fragmentation of the direct map was one of the major concerns raised during the previous postings, I've added an amortizing cache of PMD-size pages to each file descriptor that is used as an allocation pool for the secret memory areas. v5: https://lore.kernel.org/lkml/20200916073539.3552-1-rppt@kernel.org v4: https://lore.kernel.org/lkml/20200818141554.13945-1-rppt@kernel.org v3: https://lore.kernel.org/lkml/20200804095035.18778-1-rppt@kernel.org v2: https://lore.kernel.org/lkml/20200727162935.31714-1-rppt@kernel.org v1: https://lore.kernel.org/lkml/20200720092435.17469-1-rppt@kernel.org Mike Rapoport (6): mm: add definition of PMD_PAGE_ORDER mmap: make mlock_future_check() global mm: introduce memfd_secret system call to create "secret" memory areas arch, mm: wire up memfd_secret system call were relevant mm: secretmem: use PMD-size pages to amortize direct map fragmentation secretmem: test: add basic selftest for memfd_secret(2) arch/Kconfig | 7 + arch/arm64/include/asm/unistd.h | 2 +- arch/arm64/include/asm/unistd32.h | 2 + arch/arm64/include/uapi/asm/unistd.h | 1 + arch/riscv/include/asm/unistd.h | 1 + arch/x86/Kconfig | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + fs/dax.c | 11 +- include/linux/pgtable.h | 3 + include/linux/syscalls.h | 1 + include/uapi/asm-generic/unistd.h | 7 +- include/uapi/linux/magic.h | 1 + include/uapi/linux/secretmem.h | 8 + kernel/sys_ni.c | 2 + mm/Kconfig | 4 + mm/Makefile | 1 + mm/internal.h | 3 + mm/mmap.c | 5 +- mm/secretmem.c | 333 ++++++++++++++++++++++ scripts/checksyscalls.sh | 4 + tools/testing/selftests/vm/.gitignore | 1 + tools/testing/selftests/vm/Makefile | 3 +- tools/testing/selftests/vm/memfd_secret.c | 296 +++++++++++++++++++ tools/testing/selftests/vm/run_vmtests | 17 ++ 25 files changed, 703 insertions(+), 13 deletions(-) create mode 100644 include/uapi/linux/secretmem.h create mode 100644 mm/secretmem.c create mode 100644 tools/testing/selftests/vm/memfd_secret.c Acked-by: Hagen Paul Pfeifer