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 0E4CBC678D4 for ; Thu, 19 Jan 2023 01:14:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229987AbjASBOD (ORCPT ); Wed, 18 Jan 2023 20:14:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37414 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229813AbjASBNp (ORCPT ); Wed, 18 Jan 2023 20:13:45 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 97AA969B1A for ; Wed, 18 Jan 2023 17:13:37 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E3A66B81FBC for ; Thu, 19 Jan 2023 01:13:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85B33C433D2; Thu, 19 Jan 2023 01:13:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1674090814; bh=s4tyzjF7R6rTR9GGwv1/dtpajL5wYIBkwrLVapBU9K4=; h=Date:To:From:Subject:From; b=gebYctQ55jiueY+Kf9d9/TI4XToqYgplzm5XE4fu3NFj/xmFj4GV/TLiszu9T4s+h rHUsCXZJyEukjSfzgyo5uwSiQSv/PbBlqRURqeXxWl4e8Tj8Ztr3/prY7Rz3opG073 jsUg4QeyMJWWA0coGk2vjl1ZpJMXR0wOKXdQs1qk= Date: Wed, 18 Jan 2023 17:13:34 -0800 To: mm-commits@vger.kernel.org, skhan@linuxfoundation.org, lkp@intel.com, keescook@chromium.org, jorgelo@chromium.org, jeffxu@google.com, jannh@google.com, hughd@google.com, dmitry.torokhov@gmail.com, dh.herrmann@gmail.com, dverkamp@chromium.org, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-memfd-add-f_seal_exec.patch removed from -mm tree Message-Id: <20230119011334.85B33C433D2@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: mm/memfd: add F_SEAL_EXEC has been removed from the -mm tree. Its filename was mm-memfd-add-f_seal_exec.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Daniel Verkamp Subject: mm/memfd: add F_SEAL_EXEC Date: Thu, 15 Dec 2022 00:12:01 +0000 Patch series "mm/memfd: introduce MFD_NOEXEC_SEAL and MFD_EXEC", v8. 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 patch (of 5): The new F_SEAL_EXEC flag will prevent modification of the exec bits: written as traditional octal mask, 0111, or as named flags, S_IXUSR | S_IXGRP | S_IXOTH. Any chmod(2) or similar call that attempts to modify any of these bits after the seal is applied will fail with errno EPERM. This will preserve the execute bits as they are at the time of sealing, so the memfd will become either permanently executable or permanently un-executable. Link: https://lkml.kernel.org/r/20221215001205.51969-1-jeffxu@google.com Link: https://lkml.kernel.org/r/20221215001205.51969-2-jeffxu@google.com Signed-off-by: Daniel Verkamp Co-developed-by: Jeff Xu Signed-off-by: Jeff Xu Reviewed-by: Kees Cook Cc: Dmitry Torokhov Cc: Hugh Dickins Cc: Jann Horn Cc: Jorge Lucangeli Obes Cc: Shuah Khan Cc: David Herrmann Cc: kernel test robot Signed-off-by: Andrew Morton --- include/uapi/linux/fcntl.h | 1 + mm/memfd.c | 2 ++ mm/shmem.c | 6 ++++++ 3 files changed, 9 insertions(+) --- a/include/uapi/linux/fcntl.h~mm-memfd-add-f_seal_exec +++ a/include/uapi/linux/fcntl.h @@ -43,6 +43,7 @@ #define F_SEAL_GROW 0x0004 /* prevent file from growing */ #define F_SEAL_WRITE 0x0008 /* prevent writes */ #define F_SEAL_FUTURE_WRITE 0x0010 /* prevent future writes while mapped */ +#define F_SEAL_EXEC 0x0020 /* prevent chmod modifying exec bits */ /* (1U << 31) is reserved for signed error codes */ /* --- a/mm/memfd.c~mm-memfd-add-f_seal_exec +++ a/mm/memfd.c @@ -147,6 +147,7 @@ static unsigned int *memfd_file_seals_pt } #define F_ALL_SEALS (F_SEAL_SEAL | \ + F_SEAL_EXEC | \ F_SEAL_SHRINK | \ F_SEAL_GROW | \ F_SEAL_WRITE | \ @@ -175,6 +176,7 @@ static int memfd_add_seals(struct file * * SEAL_SHRINK: Prevent the file from shrinking * SEAL_GROW: Prevent the file from growing * SEAL_WRITE: Prevent write access to the file + * SEAL_EXEC: Prevent modification of the exec bits in the file mode * * As we don't require any trust relationship between two parties, we * must prevent seals from being removed. Therefore, sealing a file --- a/mm/shmem.c~mm-memfd-add-f_seal_exec +++ a/mm/shmem.c @@ -1093,6 +1093,12 @@ static int shmem_setattr(struct user_nam if (error) return error; + if ((info->seals & F_SEAL_EXEC) && (attr->ia_valid & ATTR_MODE)) { + if ((inode->i_mode ^ attr->ia_mode) & 0111) { + return -EPERM; + } + } + if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) { loff_t oldsize = inode->i_size; loff_t newsize = attr->ia_size; _ Patches currently in -mm which might be from dverkamp@chromium.org are