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 X-Spam-Level: X-Spam-Status: No, score=-11.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F53DC433E0 for ; Wed, 23 Dec 2020 01:58:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4084F22571 for ; Wed, 23 Dec 2020 01:58:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726413AbgLWB6Q (ORCPT ); Tue, 22 Dec 2020 20:58:16 -0500 Received: from mga06.intel.com ([134.134.136.31]:49021 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726361AbgLWB6Q (ORCPT ); Tue, 22 Dec 2020 20:58:16 -0500 IronPort-SDR: 6/5/hEI65WYj41wI9AjeK0K8Sw31TSmCAF0vpOJQa/wmDTtp2dTW2gDU5BAbvCW11Wku9+ytCj 0ZI9gVN0ikSA== X-IronPort-AV: E=McAfee;i="6000,8403,9843"; a="237508790" X-IronPort-AV: E=Sophos;i="5.78,440,1599548400"; d="scan'208";a="237508790" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Dec 2020 17:57:34 -0800 IronPort-SDR: yKGf3adYatD3eoY0tuXwgz1+NJhRrMtTFTzMfHezOqij4PZBXBtISpD1hyJUM8IP5GEQlaQXYY CdJHd91uQlVQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.78,440,1599548400"; d="scan'208";a="457755715" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga001.fm.intel.com with ESMTP; 22 Dec 2020 17:57:33 -0800 From: "Chang S. Bae" To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Cc: len.brown@intel.com, dave.hansen@intel.com, hjl.tools@gmail.com, Dave.Martin@arm.com, jannh@google.com, mpe@ellerman.id.au, tony.luck@intel.com, ravi.v.shankar@intel.com, libc-alpha@sourceware.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, chang.seok.bae@intel.com Subject: [PATCH v3 0/4] x86: Improve Minimum Alternate Stack Size Date: Tue, 22 Dec 2020 17:53:08 -0800 Message-Id: <20201223015312.4882-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org During signal entry, the kernel pushes data onto the normal userspace stack. On x86, the data pushed onto the user stack includes XSAVE state, which has grown over time as new features and larger registers have been added to the architecture. MINSIGSTKSZ is a constant provided in the kernel signal.h headers and typically distributed in lib-dev(el) packages, e.g. [1]. Its value is compiled into programs and is part of the user/kernel ABI. The MINSIGSTKSZ constant indicates to userspace how much data the kernel expects to push on the user stack, [2][3]. However, this constant is much too small and does not reflect recent additions to the architecture. For instance, when AVX-512 states are in use, the signal frame size can be 3.5KB while MINSIGSTKSZ remains 2KB. The bug report [4] explains this as an ABI issue. The small MINSIGSTKSZ can cause user stack overflow when delivering a signal. In this series, we suggest a couple of things: 1. Provide a variable minimum stack size to userspace, as a similar approach to [5] 2. Avoid using a too-small alternate stack Changes from v2 [7]: * Simplified the sigaltstack overflow prevention (Jann Horn) * Renamed fpstate size helper with cleanup (Borislav Petkov) * Cleaned up the signframe struct size defines (Borislav Petkov) * Revised the selftest messages (Borislav Petkov) * Revised a changelog (Borislav Petkov) Changes from v1 [6]: * Took stack alignment into account for sigframe size (Dave Martin) [1]: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/bits/sigstack.h;h=b9dca794da093dc4d41d39db9851d444e1b54d9b;hb=HEAD [2]: https://www.gnu.org/software/libc/manual/html_node/Signal-Stack.html [3]: https://man7.org/linux/man-pages/man2/sigaltstack.2.html [4]: https://bugzilla.kernel.org/show_bug.cgi?id=153531 [5]: https://blog.linuxplumbersconf.org/2017/ocw/system/presentations/4671/original/plumbers-dm-2017.pdf [6]: https://lore.kernel.org/lkml/20200929205746.6763-1-chang.seok.bae@intel.com/ [7]: https://lore.kernel.org/lkml/20201119190237.626-1-chang.seok.bae@intel.com/ Chang S. Bae (4): x86/signal: Introduce helpers to get the maximum signal frame size x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ x86/signal: Prevent an alternate stack overflow before a signal delivery selftest/x86/signal: Include test cases for validating sigaltstack arch/x86/include/asm/elf.h | 4 + arch/x86/include/asm/fpu/signal.h | 2 + arch/x86/include/asm/sigframe.h | 2 + arch/x86/include/uapi/asm/auxvec.h | 6 +- arch/x86/kernel/cpu/common.c | 3 + arch/x86/kernel/fpu/signal.c | 19 ++++ arch/x86/kernel/signal.c | 69 +++++++++++- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigaltstack.c | 128 ++++++++++++++++++++++ 9 files changed, 228 insertions(+), 7 deletions(-) create mode 100644 tools/testing/selftests/x86/sigaltstack.c -- 2.17.1