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 5AB2EC04E69 for ; Thu, 10 Aug 2023 17:20:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234929AbjHJRUf (ORCPT ); Thu, 10 Aug 2023 13:20:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234847AbjHJRUe (ORCPT ); Thu, 10 Aug 2023 13:20:34 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03D382705; Thu, 10 Aug 2023 10:20:34 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 930486140D; Thu, 10 Aug 2023 17:20:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 45F14C433C8; Thu, 10 Aug 2023 17:20:28 +0000 (UTC) Date: Thu, 10 Aug 2023 18:20:25 +0100 From: Catalin Marinas To: Mark Brown Cc: Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Kees Cook , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v4 11/36] arm64/mm: Map pages for guarded control stack Message-ID: References: <20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org> <20230807-arm64-gcs-v4-11-68cfa37f9069@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230807-arm64-gcs-v4-11-68cfa37f9069@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Aug 07, 2023 at 11:00:16PM +0100, Mark Brown wrote: > diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c > index 8f5b7ce857ed..8f40198cd44e 100644 > --- a/arch/arm64/mm/mmap.c > +++ b/arch/arm64/mm/mmap.c > @@ -79,8 +79,18 @@ arch_initcall(adjust_protection_map); > > pgprot_t vm_get_page_prot(unsigned long vm_flags) > { > - pteval_t prot = pgprot_val(protection_map[vm_flags & > + pteval_t prot; > + > + /* If this is a GCS then only interpret VM_WRITE. */ > + if (system_supports_gcs() && (vm_flags & VM_SHADOW_STACK)) { > + if (vm_flags & VM_WRITE) > + prot = _PAGE_GCS; > + else > + prot = _PAGE_GCS_RO; > + } else { > + prot = pgprot_val(protection_map[vm_flags & > (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]); > + } > > if (vm_flags & VM_ARM64_BTI) > prot |= PTE_GP; Some combinations here don't make sense like GCS + exec or BTI. I think the code above (correctly) ignores exec but it still sets PTE_GP if BTI (the architecture may allow this but you can't execute from the GCS page anyway). I haven't checked the x86 patches to see when VM_SHADOW_STACK is set but if there's no additional check at a higher level, we should add something to arch_validate_flags(), assuming it's called on those paths. -- Catalin