From patchwork Wed Feb 3 17:22:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 41918 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id E43733857005; Wed, 3 Feb 2021 17:27:24 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E43733857005 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1612373245; bh=ICaaAckZe8vjArTxUqdepO+5CB+mWx270JL9SQRDg/E=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=JosLGAaANfki3oICLKC3BYmf++TFsPje9JeSjk707DnAv2tVvoFzB1G9rPILM267P H5z9zFTw8DX+OBMq3zBvemNF2kXOfOmmOARu7xnJlqUhEnRZRnPE6LAHypqlweHl7Z dAVVyJ2tcuWsADocAsZl1c+VdSgzuaKKwB5NxoLM= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by sourceware.org (Postfix) with ESMTPS id EC956393C858 for ; Wed, 3 Feb 2021 17:27:21 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org EC956393C858 IronPort-SDR: uq0JXmFq8iRrcRreJ8Gm9wMxn8UP6wZHuD6ECPDKPlvFlFBxQsdQVmbq/2wCL3Zzt/YIhEjie5 hkPQeW7+LqNg== X-IronPort-AV: E=McAfee;i="6000,8403,9884"; a="180310458" X-IronPort-AV: E=Sophos;i="5.79,399,1602572400"; d="scan'208";a="180310458" Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 03 Feb 2021 09:27:19 -0800 IronPort-SDR: oA3PaKU9GGXLkN4skpI8G0zZ4UhSSLoR9DRe6hQucbEG5o+5YjsqiWfNaxB3rPrX2+LHoGRZ/K mexo0SkdBtGA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,399,1602572400"; d="scan'208";a="406723651" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga004.fm.intel.com with ESMTP; 03 Feb 2021 09:27:19 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v5 0/5] x86: Improve Minimum Alternate Stack Size Date: Wed, 3 Feb 2021 09:22:37 -0800 Message-Id: <20210203172242.29644-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 X-Spam-Status: No, score=-2.8 required=5.0 tests=AC_FROM_MANY_DOTS, BAYES_00, KAM_DMARC_STATUS, KAM_SHORT, PDS_BTC_ID, PDS_LITECOIN_ID, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, dave.hansen@intel.com, linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" 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 v4 [9]: * Moved the aux vector define to the generic header (Carlos O'Donell) Changes from v3 [8]: * Updated the changelog (Borislav Petkov) * Revised the test messages again (Borislav Petkov) 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=b9dca794da09 3dc4d41d39db9851d444e1b54d9b;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/ [8]: https://lore.kernel.org/lkml/20201223015312.4882-1-chang.seok.bae@intel.com/ [9]: https://lore.kernel.org/lkml/20210115211038.2072-1-chang.seok.bae@intel.com/ Chang S. Bae (5): uapi: Move the aux vector AT_MINSIGSTKSZ define to uapi x86/signal: Introduce helpers to get the maximum signal frame size x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ x86/signal: Detect and prevent an alternate signal stack overflow selftest/x86/signal: Include test cases for validating sigaltstack arch/arm64/include/uapi/asm/auxvec.h | 1 - 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 | 4 +- arch/x86/kernel/cpu/common.c | 3 + arch/x86/kernel/fpu/signal.c | 19 ++++ arch/x86/kernel/signal.c | 69 +++++++++++- include/uapi/linux/auxvec.h | 1 + tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigaltstack.c | 128 ++++++++++++++++++++++ 11 files changed, 227 insertions(+), 8 deletions(-) create mode 100644 tools/testing/selftests/x86/sigaltstack.c