From patchwork Thu Oct 31 16:46:20 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 11221559 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 55B2D1599 for ; Thu, 31 Oct 2019 16:46:50 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2DAA42190F for ; Thu, 31 Oct 2019 16:46:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Du+LxYfw"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=google.com header.i=@google.com header.b="X72pCBme" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2DAA42190F Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:To:From:Subject:References:Mime-Version :Message-Id:In-Reply-To:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=tK9swOyO6RJ+GfjVippO7shmEs+XGARfXF0aXnTkR3o=; b=Du+LxYfwJDhe4b 993+OCBHiNBAq0m1IwGBv43AoBiQJGum3gcXz/fhGMfnrwqFUv+DyxrvNnHrjOFMj3taDLUs+fS0z Bv+GKGjwFwpPaOxKddfkxYQH7S2yIZ+BnIFwGHy/pZLWhmoxidogxtqhpfLxN3BOXCL29Hly5cdoP i6YKmA58skBdrdqr5u2PfGNqEH+HSp5HtbDBGNb2b56bHcO7+4FC3vg/85t8KrkpRrsWzThpN0yZE tNfremDB7Y+97gaPhlKIeE2t3in4G0N46lW+LU3NnvaIWoz1TyAQvkLXeF/6+8X+wI07FYcrdlxXD 8zclrvckn3+/6201LHSw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iQDay-0006it-Ew; Thu, 31 Oct 2019 16:46:48 +0000 Received: from mail-pf1-x449.google.com ([2607:f8b0:4864:20::449]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iQDav-0006hX-8s for linux-arm-kernel@lists.infradead.org; Thu, 31 Oct 2019 16:46:47 +0000 Received: by mail-pf1-x449.google.com with SMTP id j2so5002607pfa.8 for ; Thu, 31 Oct 2019 09:46:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=VJW4EixJ7eoVvGoW8WXB816KDrFUl4nwPba/L9J0fDM=; b=X72pCBmeu6KNeTcEZs/HbzCF3sDrWvAyivdNVRvS3VrtS/eW+94zqgHgR+xACKsx2l IC7BZebQB1kM8OaIdthHJvaTnXpdESiVK51g2vca/ejvSau2zKoF6zHNEj6ayclvX8Q1 0E8O8U2gqyQKM+wO+LwOK1nrC8kXR39u0eY6bPjpl46S90zRR0EYGAxExeEZqELG0bTT 2JMXQ0B5DcxiiehhQNhDYgQxy+Az2OiSw/2+1zKsmA+lkXmRmb5uSYLgrJnsxGNK0vuV MRtztHQTOSEh9H4fwBMfwZyJMgn8dUDLwcVKd45EdzK3pl/rwxqb7rGV7DeDmqeSm7Em OVMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=VJW4EixJ7eoVvGoW8WXB816KDrFUl4nwPba/L9J0fDM=; b=szdOYVsWzSM6a2E0X0OJ4QaFARPy4u2Wmfx9pZ7b69t+YdnLpFnfSwrq4OwJjBRNFG nAYyQ50/anDp4WmSkJG/TMBERdgrgGAVOPbmIvLsnOxHmm1yzI8b3t/vfJBrGTftiXES h73SiG9rIH7i8aveuYPX3K7MctRSKWlyrA72CQvCjiTmfPMnTXy5BjoXhc95zvLwsD+T BqJNN3ywBVkoD5SiQfYdIasQyJT5k3JmkK2GHC2Z/i00/goJOAAHS8nKmSoH1PpxUqSr nAIQP3HgMyescK8fL9X0s7KpTDiq53g77Lv+m6J+PUr1njoUC2C0Lz0jKZ1PVynEYUca V1QQ== X-Gm-Message-State: APjAAAUBDzsrjz0I0WgUEikPaM2s7JGtpEq0IrovKsHEnUs46v/yf6tK uxFttuWg/KI/kn264PSbAmpDf4hhNSpEaAIBysM= X-Google-Smtp-Source: APXvYqwNtkBpFip8q81bGhg0CvAnPTQnrqxcNvMaBe34ClJ/Yd2hlu2ZC+yn6qs00bEmTkl5AXHyjpx+Oa61GiD4Q6Q= X-Received: by 2002:a63:b95e:: with SMTP id v30mr7752425pgo.206.1572540403625; Thu, 31 Oct 2019 09:46:43 -0700 (PDT) Date: Thu, 31 Oct 2019 09:46:20 -0700 In-Reply-To: <20191018161033.261971-1-samitolvanen@google.com> Message-Id: <20191031164637.48901-1-samitolvanen@google.com> Mime-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> X-Mailer: git-send-email 2.24.0.rc0.303.g954a862665-goog Subject: [PATCH v3 00/17] add support for Clang's Shadow Call Stack From: samitolvanen@google.com To: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191031_094645_339198_0DE22DA2 X-CRM114-Status: GOOD ( 20.23 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-7.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:449 listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.0 DKIMWL_WL_MED DKIMwl.org - Medium sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Kees Cook , Jann Horn , Masahiro Yamada , kernel-hardening@lists.openwall.com, Nick Desaulniers , linux-kernel@vger.kernel.org, Miguel Ojeda , clang-built-linux@googlegroups.com, Sami Tolvanen , Laura Abbott , Dave Martin , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org This patch series adds support for Clang's Shadow Call Stack (SCS) mitigation, which uses a separately allocated shadow stack to protect against return address overwrites. More information can be found here: https://clang.llvm.org/docs/ShadowCallStack.html SCS provides better protection against traditional buffer overflows than CONFIG_STACKPROTECTOR_*, but it should be noted that SCS security guarantees in the kernel differ from the ones documented for user space. The kernel must store addresses of shadow stacks used by other tasks and interrupt handlers in memory, which means an attacker capable reading and writing arbitrary memory may be able to locate them and hijack control flow by modifying shadow stacks that are not currently in use. SCS is currently supported only on arm64, where the compiler requires the x18 register to be reserved for holding the current task's shadow stack pointer. Because of this, the series includes patches from Ard to remove x18 usage from assembly code. With -fsanitize=shadow-call-stack, the compiler injects instructions to all non-leaf C functions to store the return address to the shadow stack, and unconditionally load it again before returning. As a result, SCS is currently incompatible with features that rely on modifying function return addresses to alter control flow, such as function graph tracing and kretprobes, although it may be possible to later change these features to modify the shadow stack instead. A copy of the return address is still kept in the kernel stack for compatibility with stack unwinding, for example. SCS has a minimal performance overhead, but allocating shadow stacks increases kernel memory usage. The feature is therefore mostly useful on hardware that lacks support for PAC instructions. Changes in v3: - Switched to filter-out for removing SCS flags in Makefiles - Changed the __noscs attribute to use __no_sanitize__("...") instead of no_sanitize("...") - Cleaned up inline function definitions and moved task_scs() into a macro - Cleaned up scs_free() and scs_magic() - Moved SCS initialization into dup_task_struct() and removed the now unused scs_task_init() - Added comments to __scs_base() and scs_task_reset() to better document design choices - Changed copy_page to make the offset and bias explicit Changes in v2: - Changed Ard's KVM patch to use x29 instead of x18 for the guest context, which makes restore_callee_saved_regs cleaner - Updated help text (and commit messages) to point out differences in security properties compared to user space SCS - Cleaned up config options: removed the ROP protection choice, replaced the CC_IS_CLANG dependency with an arch-specific cc-option test, and moved disabling of incompatible config options to an arch-specific Kconfig - Added CC_FLAGS_SCS, which are filtered out where needed instead of using DISABLE_SCS - Added a __has_feature guard around __noscs for older clang versions Ard Biesheuvel (1): arm64: kernel: avoid x18 __cpu_soft_restart Sami Tolvanen (16): arm64: mm: avoid x18 in idmap_kpti_install_ng_mappings arm64/lib: copy_page: avoid x18 register in assembler code arm64: kvm: stop treating register x18 as caller save add support for Clang's Shadow Call Stack (SCS) scs: add accounting scs: add support for stack usage debugging kprobes: fix compilation without CONFIG_KRETPROBES arm64: kprobes: fix kprobes without CONFIG_KRETPROBES arm64: disable kretprobes with SCS arm64: disable function graph tracing with SCS arm64: reserve x18 from general allocation with SCS arm64: preserve x18 when CPU is suspended arm64: efi: restore x18 if it was corrupted arm64: vdso: disable Shadow Call Stack arm64: disable SCS for hypervisor code arm64: implement Shadow Call Stack Makefile | 6 + arch/Kconfig | 33 ++++ arch/arm64/Kconfig | 9 +- arch/arm64/Makefile | 4 + arch/arm64/include/asm/scs.h | 37 +++++ arch/arm64/include/asm/stacktrace.h | 4 + arch/arm64/include/asm/suspend.h | 2 +- arch/arm64/include/asm/thread_info.h | 3 + arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/asm-offsets.c | 3 + arch/arm64/kernel/cpu-reset.S | 4 +- arch/arm64/kernel/efi-rt-wrapper.S | 7 +- arch/arm64/kernel/entry.S | 28 ++++ arch/arm64/kernel/head.S | 9 ++ arch/arm64/kernel/irq.c | 2 + arch/arm64/kernel/probes/kprobes.c | 2 + arch/arm64/kernel/process.c | 2 + arch/arm64/kernel/scs.c | 39 +++++ arch/arm64/kernel/smp.c | 4 + arch/arm64/kernel/vdso/Makefile | 2 +- arch/arm64/kvm/hyp/Makefile | 3 + arch/arm64/kvm/hyp/entry.S | 41 +++-- arch/arm64/lib/copy_page.S | 38 ++--- arch/arm64/mm/proc.S | 72 +++++---- drivers/base/node.c | 6 + fs/proc/meminfo.c | 4 + include/linux/compiler-clang.h | 6 + include/linux/compiler_types.h | 4 + include/linux/mmzone.h | 3 + include/linux/scs.h | 54 +++++++ init/init_task.c | 8 + kernel/Makefile | 1 + kernel/fork.c | 9 ++ kernel/kprobes.c | 38 ++--- kernel/sched/core.c | 2 + kernel/sched/sched.h | 1 + kernel/scs.c | 227 +++++++++++++++++++++++++++ mm/page_alloc.c | 6 + mm/vmstat.c | 3 + 39 files changed, 630 insertions(+), 97 deletions(-) create mode 100644 arch/arm64/include/asm/scs.h create mode 100644 arch/arm64/kernel/scs.c create mode 100644 include/linux/scs.h create mode 100644 kernel/scs.c