From patchwork Tue May 18 20:03:14 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: 43461 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 0743E395C01D; Tue, 18 May 2021 20:08:58 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 0743E395C01D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1621368538; bh=KjRtOsSV+Ov79jfuLEilwO7umFW1ky572G/ubk3KwnE=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=b76tfIyxoqB2RwMjFHCun33Qd6h5nXRVhCEhCRUGkBnAjgc6DqDIHCAfrS75bnlhF 4S83YzrZCaXxGMrhlIQHaYAEYBrUt+DCOodA3trEgtBElOonkwFElmQmvBRy60yzYP kwovlKtlEgasWSGn3inxLGLaM//25LmPJaPoGCVo= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by sourceware.org (Postfix) with ESMTPS id 7682C385802E for ; Tue, 18 May 2021 20:08:54 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 7682C385802E IronPort-SDR: KQpeXnSnvoGl1d7wJPXPXSt5N6R6FDf0luqiPEfYmwClfEQLJNhQsbswQne1Ne2e9aEJxD5flg nvMQgtO1johg== X-IronPort-AV: E=McAfee;i="6200,9189,9988"; a="200855044" X-IronPort-AV: E=Sophos;i="5.82,310,1613462400"; d="scan'208";a="200855044" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 May 2021 13:08:51 -0700 IronPort-SDR: xdafT4k75f/m/sgHfmd/sdLJeuLxtLzTmmj1h1cbssZCNEi53P2vzGzrL5aFDykBgsLKrZ4BsR ZXt4G8f3u50A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.82,310,1613462400"; d="scan'208";a="394993611" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by orsmga006.jf.intel.com with ESMTP; 18 May 2021 13:08:51 -0700 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v9 0/6] Improve Minimum Alternate Stack Size Date: Tue, 18 May 2021 13:03:14 -0700 Message-Id: <20210518200320.17239-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 X-Spam-Status: No, score=-3.5 required=5.0 tests=AC_FROM_MANY_DOTS, BAYES_00, KAM_DMARC_STATUS, KAM_SHORT, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, 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 v8 [13]: * Added and revised some kernel messages. (Borislav Petkov) Changes from v7 [12]: * Improved the overflow check code. (Andy Lutomirski and Borislav Petkov) * Moved the "Fixes:" tag and the bugzilla link (patch 5 -> patch 3). Changes from v6 [11]: * Updated and fixed the documentation. (Borislav Petkov) * Revised the AT_MINSIGSTKSZ comment. (Borislav Petkov) Changes form v5 [10]: * Fixed the overflow detection. (Andy Lutomirski) * Reverted the AT_MINSIGSTKSZ removal on arm64. (Dave Martin) * Added a documentation about the x86 AT_MINSIGSTKSZ. * Supported the existing sigaltstack test to use the new aux vector. 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=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/ [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/ [10]: https://lore.kernel.org/lkml/20210203172242.29644-1-chang.seok.bae@intel.com/ [11]: https://lore.kernel.org/lkml/20210227165911.32757-1-chang.seok.bae@intel.com/ [12]: https://lore.kernel.org/lkml/20210316065215.23768-1-chang.seok.bae@intel.com/ [13]: https://lore.kernel.org/lkml/20210422044856.27250-1-chang.seok.bae@intel.com/ Chang S. Bae (6): uapi: Define the aux vector AT_MINSIGSTKSZ x86/signal: Introduce helpers to get the maximum signal frame size x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ selftest/sigaltstack: Use the AT_MINSIGSTKSZ aux vector if available x86/signal: Detect and prevent an alternate signal stack overflow selftest/x86/signal: Include test cases for validating sigaltstack Documentation/x86/elf_auxvec.rst | 53 +++++++++ Documentation/x86/index.rst | 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 | 88 ++++++++++++++- include/linux/sched/signal.h | 19 ++-- include/uapi/linux/auxvec.h | 3 + tools/testing/selftests/sigaltstack/sas.c | 20 +++- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigaltstack.c | 128 ++++++++++++++++++++++ 14 files changed, 327 insertions(+), 21 deletions(-) create mode 100644 Documentation/x86/elf_auxvec.rst create mode 100644 tools/testing/selftests/x86/sigaltstack.c base-commit: d07f6ca923ea0927a1024dfccafc5b53b61cfecc Acked-by: Thomas Gleixner --- 2.17.1