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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9362C64EC4 for ; Fri, 3 Mar 2023 14:00:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231165AbjCCOAa (ORCPT ); Fri, 3 Mar 2023 09:00:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231138AbjCCOA3 (ORCPT ); Fri, 3 Mar 2023 09:00:29 -0500 Received: from mail.skyhub.de (mail.skyhub.de [5.9.137.197]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8BD335C13B; Fri, 3 Mar 2023 06:00:28 -0800 (PST) Received: from zn.tnic (p5de8e9fe.dip0.t-ipconnect.de [93.232.233.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 242C31EC0657; Fri, 3 Mar 2023 15:00:27 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1677852027; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=qnYHVDGtQv3jnmqIeyy8ite/fQyg2MBE/ckQjSbBpNM=; b=YlRhGsYyfadQXHimloeHMfYzHgPMt4rRKJ5ZJpz3f7rZXiR4DcSs61vbGpJcRD7wubIbgn Cy5sYRTCmvgOgF2q8BIUBY0oGyQjXPUVKD2axEEDzT4EdiJfZum0kFSwUDEeQjb4kIYCi9 dwYF79zrOj6nrFa4wG5FeRtKoWY9ZUM= Date: Fri, 3 Mar 2023 15:00:22 +0100 From: Borislav Petkov To: Rick Edgecombe Cc: x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, david@redhat.com, debug@rivosinc.com, Yu-cheng Yu Subject: Re: [PATCH v7 19/41] x86/mm: Check shadow stack page fault errors Message-ID: References: <20230227222957.24501-1-rick.p.edgecombe@intel.com> <20230227222957.24501-20-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230227222957.24501-20-rick.p.edgecombe@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Mon, Feb 27, 2023 at 02:29:35PM -0800, Rick Edgecombe wrote: > @@ -1310,6 +1324,23 @@ void do_user_addr_fault(struct pt_regs *regs, > > perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); > > + /* > + * For conventionally writable pages, a read can be serviced with a > + * read only PTE. But for shadow stack, there isn't a concept of > + * read-only shadow stack memory. If it a PTE has the shadow stack s/it // > + * permission, it can be modified via CALL and RET instructions. So > + * core MM needs to fault in a writable PTE and do things it already > + * does for write faults. > + * > + * Shadow stack accesses (read or write) need to be serviced with > + * shadow stack permission memory, which always include write > + * permissions. So in the case of a shadow stack read access, treat it > + * as a WRITE fault. This will make sure that MM will prepare > + * everything (e.g., break COW) such that maybe_mkwrite() can create a > + * proper shadow stack PTE. > + */ > + if (error_code & X86_PF_SHSTK) > + flags |= FAULT_FLAG_WRITE; > if (error_code & X86_PF_WRITE) > flags |= FAULT_FLAG_WRITE; > if (error_code & X86_PF_INSTR) > -- > 2.17.1 > -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette