From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS17314 8.43.84.0/22 X-Spam-Status: No, score=-4.2 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server2.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id B6DBE1F5AE for ; Thu, 22 Apr 2021 04:54:28 +0000 (UTC) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 3568139BD013; Thu, 22 Apr 2021 04:54:25 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3568139BD013 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1619067265; bh=PLGyFvAbDDTNo82V+Nwf7OV/8mEIw3yJpIO8SaW4as0=; h=To:Subject:Date:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=ma1vxGziGDgnget8GM+U4InACbiMMX5QmBgxzQaf7WpGuSM021Ps2GRbzjsXi2PUN s4R+PQn9HE/SEwYDWxRYN/OeiRZtFQ4DDGtqf/VO7WIBweBaYzHQ9ObLqb/2NPvP7/ eSDEpPVHrUPbdEamyfOtAHM6UR5whK9Xi7vYr+5I= Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by sourceware.org (Postfix) with ESMTPS id DFC8E385801A for ; Thu, 22 Apr 2021 04:54:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org DFC8E385801A IronPort-SDR: JtXr1VcRQLQgCoxG9KtSk+/gaXHLU5oXevbDSoreTY+/7KFreuqUXCD3juRPfGaiBos0cUH0kE A/8JTBh4JV1w== X-IronPort-AV: E=McAfee;i="6200,9189,9961"; a="175312062" X-IronPort-AV: E=Sophos;i="5.82,241,1613462400"; d="scan'208";a="175312062" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Apr 2021 21:54:15 -0700 IronPort-SDR: ng6S2uhXBznN5B0MM96aBEwTBWUcbVAFaDgSc9AVtjE6RhWMJE6EIKStQy9cVOoG0VY36i28D5 SBXu3O9fSr+A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.82,241,1613462400"; d="scan'208";a="524515397" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga001.fm.intel.com with ESMTP; 21 Apr 2021 21:54:15 -0700 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v8 0/6] Improve Minimum Alternate Stack Size Date: Wed, 21 Apr 2021 21:48:50 -0700 Message-Id: <20210422044856.27250-1-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 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: , From: "Chang S. Bae via Libc-alpha" 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 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/ 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 | 86 ++++++++++++++- 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, 325 insertions(+), 21 deletions(-) create mode 100644 Documentation/x86/elf_auxvec.rst create mode 100644 tools/testing/selftests/x86/sigaltstack.c base-commit: bf05bf16c76bb44ab5156223e1e58e26dfe30a88 -- 2.17.1