From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8FB23C63707 for ; Wed, 7 Dec 2022 15:49:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229678AbiLGPtv (ORCPT ); Wed, 7 Dec 2022 10:49:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50614 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229603AbiLGPtq (ORCPT ); Wed, 7 Dec 2022 10:49:46 -0500 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A14024951 for ; Wed, 7 Dec 2022 07:49:45 -0800 (PST) Received: by mail-pj1-x102e.google.com with SMTP id t11-20020a17090a024b00b0021932afece4so1814352pje.5 for ; Wed, 07 Dec 2022 07:49:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=SebK6VeMwVI8zNPc+AGDZ/foDvzVT7LenZ1q5aL6Vd0=; b=bXpIMlKZLOugUItEp+yK3IZEPErrpxgFQ3yGo+icXLxideMkE4N9Fl1V9tRqJmVJKL kkGO+i3x5P4gqnCUXgxjG6vCaQUG4ifV0IyOaZqXC1wAIy4PoD6cdcnJ+oJrZBc/aqiq xPr95nZlhxEuoy7lqLgIC5sVkXFhlAxbDK/BU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=SebK6VeMwVI8zNPc+AGDZ/foDvzVT7LenZ1q5aL6Vd0=; b=edY1uHiJ02H+fb9Gjv3Bf0SPswxBV1qLY1X8i7MaDNuqnXZ/QYsBw0+TOx4AeopMG5 8OdbBM5LyTlZSwMn3MG6s0dubfwkA6hNb1L4ah5ooq1ORL7WOqbpqoBD6IqW4RR2R7Zh I4Hqhj7oOzIFjWPYwvX6eIfanmEyXXmB3DhuKk+N0dtGs99LFBZQaAGmh2h/wYqAa/vh UdWvv3hmoSdJIERQohQreDEvUxpxSAARKxqpgGOLGRGKovd3wXwNfsySdCqQemhdYQLc SNA7ugwTnWJlrUoxsUt1S78zSetaCgFmgIxyA+K3mRW+YgwczC+kg9TdLxX1ahT38PAK hEFw== X-Gm-Message-State: ANoB5pkvCGw2TKXDj1Q6AYganIQdd35YaVDBv2o4pnXElcplwvBvALNu gGfsQkNTDLHWnOqC8c5EFjlSKw== X-Google-Smtp-Source: AA0mqf7DJw1rIWEXKC49n6cPVKA1w2gt+CVOmiPUQGyrAdU+wzfuFVLdh+Ap0uUT4HhJtSSro1Heww== X-Received: by 2002:a17:902:9a82:b0:189:e085:8416 with SMTP id w2-20020a1709029a8200b00189e0858416mr714393plp.17.1670428184683; Wed, 07 Dec 2022 07:49:44 -0800 (PST) Received: from jeffxud.c.googlers.com.com (30.202.168.34.bc.googleusercontent.com. [34.168.202.30]) by smtp.gmail.com with ESMTPSA id a9-20020a170902ecc900b0017f7628cbddsm14920934plh.30.2022.12.07.07.49.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 Dec 2022 07:49:44 -0800 (PST) From: jeffxu@chromium.org To: skhan@linuxfoundation.org, keescook@chromium.org Cc: akpm@linux-foundation.org, dmitry.torokhov@gmail.com, dverkamp@chromium.org, hughd@google.com, jeffxu@google.com, jorgelo@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, jannh@google.com, linux-hardening@vger.kernel.org Subject: [PATCH v6 0/6] mm/memfd: introduce MFD_NOEXEC_SEAL and MFD_EXEC Date: Wed, 7 Dec 2022 15:49:33 +0000 Message-Id: <20221207154939.2532830-1-jeffxu@google.com> X-Mailer: git-send-email 2.39.0.rc0.267.gcb52ba06e7-goog MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jeff Xu Since Linux introduced the memfd feature, memfd have always had their execute bit set, and the memfd_create() syscall doesn't allow setting it differently. However, in a secure by default system, such as ChromeOS, (where all executables should come from the rootfs, which is protected by Verified boot), this executable nature of memfd opens a door for NoExec bypass and enables “confused deputy attack”. E.g, in VRP bug [1]: cros_vm process created a memfd to share the content with an external process, however the memfd is overwritten and used for executing arbitrary code and root escalation. [2] lists more VRP in this kind. On the other hand, executable memfd has its legit use, runc uses memfd’s seal and executable feature to copy the contents of the binary then execute them, for such system, we need a solution to differentiate runc's use of executable memfds and an attacker's [3]. To address those above, this set of patches add following: 1> Let memfd_create() set X bit at creation time. 2> Let memfd to be sealed for modifying X bit. 3> A new pid namespace sysctl: vm.memfd_noexec to control the behavior of X bit.For example, if a container has vm.memfd_noexec=2, then memfd_create() without MFD_NOEXEC_SEAL will be rejected. 4> A new security hook in memfd_create(). This make it possible to a new LSM, which rejects or allows executable memfd based on its security policy. This is V6 version of patch: see [4] [5] [6] [7] for previous versions. [1] https://crbug.com/1305411 [2] https://bugs.chromium.org/p/chromium/issues/list?q=type%3Dbug-security%20memfd%20escalation&can=1 [3] https://lwn.net/Articles/781013/ [4] https://lwn.net/Articles/890096/ [5] https://lore.kernel.org/lkml/20220805222126.142525-1-jeffxu@google.com/ [6] https://lore.kernel.org/lkml/20221202013404.163143-1-jeffxu@google.com/ [7] https://lore.kernel.org/lkml/20221206152358.1966099-1-jeffxu@google.com/ Daniel Verkamp (2): mm/memfd: add F_SEAL_EXEC selftests/memfd: add tests for F_SEAL_EXEC Jeff Xu (4): mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC mm/memfd: Add write seals when apply SEAL_EXEC to executable memfd selftests/memfd: add tests for MFD_NOEXEC_SEAL MFD_EXEC mm/memfd: security hook for memfd_create include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 4 + include/linux/pid_namespace.h | 19 ++ include/linux/security.h | 6 + include/uapi/linux/fcntl.h | 1 + include/uapi/linux/memfd.h | 4 + kernel/pid_namespace.c | 5 + kernel/pid_sysctl.h | 59 ++++ mm/memfd.c | 61 +++- mm/shmem.c | 6 + security/security.c | 13 + tools/testing/selftests/memfd/fuse_test.c | 1 + tools/testing/selftests/memfd/memfd_test.c | 348 ++++++++++++++++++++- 13 files changed, 525 insertions(+), 3 deletions(-) create mode 100644 kernel/pid_sysctl.h base-commit: eb7081409f94a9a8608593d0fb63a1aa3d6f95d8 -- 2.39.0.rc0.267.gcb52ba06e7-goog