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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 9AB0CC433FE for ; Fri, 7 Oct 2022 11:31:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bPa4xqyb8PpxUI5ngi8tKdVMaPcakfH3wXy0czY/QY8=; b=v2KGnNTU0V6m6T ssJ2iNjcawBCaXX5jl/9PHUte5BenH5zs4vFUP56gd3DSnpdzjcoQqIKLAWl4FqgJIQN7wVtFgKZn b0BnLFbk5ZpHrl8fzjaRQbrCCe2vWou0x+Ie78wejORT33S+jQAe6rg7fMccMJf4JWASd+AAF6sed oL8wyApG2BiXnpNZwO6kmcH8rCOZ6USMHWY7UWfQZXqX5Cjn8YD3Q237OyvUai3KMAgsvPTKKlkIA WfhFkk4+3wFMmgdPefyw1fu2p7qPlQcEfrppTxLN7Jh1DsM89L+sOKg6z0pomIux9fs2wdhNPpAz7 MW+Ne2YdCGcj55vW6+EA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oglYW-008h5Z-Ah; Fri, 07 Oct 2022 11:30:16 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oglYQ-008h4e-Go; Fri, 07 Oct 2022 11:30:12 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 746711063; Fri, 7 Oct 2022 04:30:10 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 695033F792; Fri, 7 Oct 2022 04:30:00 -0700 (PDT) Date: Fri, 7 Oct 2022 12:29:49 +0100 From: Mark Rutland To: Palmer Dabbelt Cc: Conor.Dooley@microchip.com, guoren@kernel.org, oleg@redhat.com, vgupta@kernel.org, linux@armlinux.org.uk, monstr@monstr.eu, dinguyen@kernel.org, davem@davemloft.net, Arnd Bergmann , shorne@gmail.com, Paul Walmsley , aou@eecs.berkeley.edu, ardb@kernel.org, heiko@sntech.de, daolu@rivosinc.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, sparclinux@vger.kernel.org, openrisc@lists.librecores.org, xianting.tian@linux.alibaba.com, linux-efi@vger.kernel.org Subject: Re: [PATCH] RISC-V: Add STACKLEAK erasing the kernel stack at the end of syscalls Message-ID: References: <6c48657c-04df-132d-6167-49ed293dea44@microchip.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221007_043010_670709_FE4431A3 X-CRM114-Status: GOOD ( 21.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Oct 06, 2022 at 07:31:01PM -0700, Palmer Dabbelt wrote: > On Tue, 06 Sep 2022 10:35:10 PDT (-0700), Conor.Dooley@microchip.com wrote: > > On 03/09/2022 17:23, guoren@kernel.org wrote: > > > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > > > > > From: Xianting Tian > > > > > > This adds support for the STACKLEAK gcc plugin to RISC-V and disables > > > the plugin in EFI stub code, which is out of scope for the protection. > > > > > > For the benefits of STACKLEAK feature, please check the commit > > > afaef01c0015 ("x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls") > > > > > > Performance impact (tested on qemu env with 1 riscv64 hart, 1GB mem) > > > hackbench -s 512 -l 200 -g 15 -f 25 -P > > > 2.0% slowdown > > > > > > Signed-off-by: Xianting Tian > > > > What changed since Xianting posted it himself a week ago: > > https://lore.kernel.org/linux-riscv/20220828135407.3897717-1-xianting.tian@linux.alibaba.com/ > > > > There's an older patch from Du Lao adding STACKLEAK too: > > https://lore.kernel.org/linux-riscv/20220615213834.3116135-1-daolu@rivosinc.com/ > > > > But since there's been no activity there since June... > > Looks like the only issues were some commit log wording stuff, and that > there's a test suite that should be run. It's not clear from the commits > that anyone has done that, I'm fine with the patch if it passes the tests > but don't really know how to run them. Enable CONFIG_LKDTM, and do: echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT Example GOOD/BAD output below, taken from: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/misc/lkdtm/stackleak.c?id=72b61896f2b47fa4b98e86184bc0e6ddbd1a8db1 GOOD result on x86_64: | # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT | lkdtm: Performing direct entry STACKLEAK_ERASING | lkdtm: stackleak stack usage: | high offset: 168 bytes | current: 336 bytes | lowest: 656 bytes | tracked: 656 bytes | untracked: 400 bytes | poisoned: 15152 bytes | low offset: 8 bytes | lkdtm: OK: the rest of the thread stack is properly erased GOOD result on arm64: | # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT | lkdtm: Performing direct entry STACKLEAK_ERASING | lkdtm: stackleak stack usage: | high offset: 336 bytes | current: 656 bytes | lowest: 1232 bytes | tracked: 1232 bytes | untracked: 672 bytes | poisoned: 14136 bytes | low offset: 8 bytes | lkdtm: OK: the rest of the thread stack is properly erased BAD result on arm64: | # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT | lkdtm: Performing direct entry STACKLEAK_ERASING | lkdtm: FAIL: non-poison value 24 bytes below poison boundary: 0x0 | lkdtm: FAIL: non-poison value 32 bytes below poison boundary: 0xffff8000083dbc00 ... | lkdtm: FAIL: non-poison value 1912 bytes below poison boundary: 0x78b4b9999e8cb15 | lkdtm: FAIL: non-poison value 1920 bytes below poison boundary: 0xffff8000083db400 | lkdtm: stackleak stack usage: | high offset: 336 bytes | current: 688 bytes | lowest: 1232 bytes | tracked: 576 bytes | untracked: 288 bytes | poisoned: 15176 bytes | low offset: 8 bytes | lkdtm: FAIL: the thread stack is NOT properly erased! | lkdtm: Unexpected! This kernel (5.18.0-rc1-00013-g1f7b1f1e29e0-dirty aarch64) was built with CONFIG_GCC_PLUGIN_STACKLEAK=y Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel