From patchwork Tue Dec 21 15:11:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chao Peng X-Patchwork-Id: 12689901 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 BA638C4332F for ; Tue, 21 Dec 2021 15:12:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239032AbhLUPM1 (ORCPT ); Tue, 21 Dec 2021 10:12:27 -0500 Received: from mga05.intel.com ([192.55.52.43]:21249 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239021AbhLUPM0 (ORCPT ); Tue, 21 Dec 2021 10:12:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1640099546; x=1671635546; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=L6zzX+w0dRm95JSP/7w36iYjjnEIWuQgAZ4mQ5a+0Og=; b=IEDR41bSErwwopU7CNwh/2ylxv4g5N3Lw3YIvWzRi8usffwArkzit550 4148DOv0EzrrsTD+LDZl+pf1vyxF6xhGw5Vfio+hMkNLJ5fuE5SbpUfxt E9ZIa4Dk5lsVLDsoO50qkUaB5lZM/A2m0zoZ5hvaSvb2qCBvmLWSakGbp Fas0zQCDjGTv+SOyDGhQL2dQZu5qeU0bXqanmRQgP5hUMvnRCDbx/1g3E Y0uxYut+4C2NTsylHqwB3RcSELDJxd6go9Ex924yHhFwnzSkbjHkEMkNi AmNE9SjKci11oeHC2bKKStNETN7Qm3CGX7qGMR6LfViP8OwpeYg9M6l/g w==; X-IronPort-AV: E=McAfee;i="6200,9189,10204"; a="326709670" X-IronPort-AV: E=Sophos;i="5.88,223,1635231600"; d="scan'208";a="326709670" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Dec 2021 07:12:26 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,223,1635231600"; d="scan'208";a="684688307" Received: from chaop.bj.intel.com ([10.240.192.101]) by orsmga005.jf.intel.com with ESMTP; 21 Dec 2021 07:12:18 -0800 From: Chao Peng To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, qemu-devel@nongnu.org Cc: Paolo Bonzini , Jonathan Corbet , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H . Peter Anvin" , Hugh Dickins , Jeff Layton , "J . Bruce Fields" , Andrew Morton , Yu Zhang , Chao Peng , "Kirill A . Shutemov" , luto@kernel.org, john.ji@intel.com, susie.li@intel.com, jun.nakajima@intel.com, dave.hansen@intel.com, ak@linux.intel.com, david@redhat.com Subject: [PATCH v3 02/15] mm/memfd: Introduce MFD_INACCESSIBLE flag Date: Tue, 21 Dec 2021 23:11:12 +0800 Message-Id: <20211221151125.19446-3-chao.p.peng@linux.intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20211221151125.19446-1-chao.p.peng@linux.intel.com> References: <20211221151125.19446-1-chao.p.peng@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Introduce a new memfd_create() flag indicating the content of the created memfd is inaccessible from userspace. It does this by force setting F_SEAL_INACCESSIBLE seal when the file is created. It also set F_SEAL_SEAL to prevent future sealing, which means, it can not coexist with MFD_ALLOW_SEALING. Signed-off-by: Chao Peng --- include/uapi/linux/memfd.h | 1 + mm/memfd.c | 12 +++++++++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/memfd.h b/include/uapi/linux/memfd.h index 7a8a26751c23..48750474b904 100644 --- a/include/uapi/linux/memfd.h +++ b/include/uapi/linux/memfd.h @@ -8,6 +8,7 @@ #define MFD_CLOEXEC 0x0001U #define MFD_ALLOW_SEALING 0x0002U #define MFD_HUGETLB 0x0004U +#define MFD_INACCESSIBLE 0x0008U /* * Huge page size encoding when MFD_HUGETLB is specified, and a huge page diff --git a/mm/memfd.c b/mm/memfd.c index 9f80f162791a..c898a007fb76 100644 --- a/mm/memfd.c +++ b/mm/memfd.c @@ -245,7 +245,8 @@ long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg) #define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1) #define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN) -#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB) +#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB | \ + MFD_INACCESSIBLE) SYSCALL_DEFINE2(memfd_create, const char __user *, uname, @@ -267,6 +268,10 @@ SYSCALL_DEFINE2(memfd_create, return -EINVAL; } + /* Disallow sealing when MFD_INACCESSIBLE is set. */ + if (flags & MFD_INACCESSIBLE && flags & MFD_ALLOW_SEALING) + return -EINVAL; + /* length includes terminating zero */ len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1); if (len <= 0) @@ -315,6 +320,11 @@ SYSCALL_DEFINE2(memfd_create, *file_seals &= ~F_SEAL_SEAL; } + if (flags & MFD_INACCESSIBLE) { + file_seals = memfd_file_seals_ptr(file); + *file_seals &= F_SEAL_SEAL | F_SEAL_INACCESSIBLE; + } + fd_install(fd, file); kfree(name); return fd;