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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B69D7C3DA4A for ; Thu, 22 Aug 2024 16:12:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BC4AF6B02F2; Thu, 22 Aug 2024 12:12:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AFEB66B02F3; Thu, 22 Aug 2024 12:12:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9520A6B02F4; Thu, 22 Aug 2024 12:12:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 6BDCA6B02F2 for ; Thu, 22 Aug 2024 12:12:48 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 080931A0BE8 for ; Thu, 22 Aug 2024 16:12:47 +0000 (UTC) X-FDA: 82480374774.11.CE582C2 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf30.hostedemail.com (Postfix) with ESMTP id A8DE580028 for ; Thu, 22 Aug 2024 16:12:44 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=none; spf=pass (imf30.hostedemail.com: domain of cmarinas@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724343125; h=from:from:sender: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=r49/SqVIJ1L2MDEKT/MRvDwnYSz44Se8FlYvjbDRefA=; b=h4Gka3pYe9Av/SwZtEo8Pb6zrXGSaUHP694m1VeZWjOa01CnpdPhmBG2R/LjiQfWKlF7IN n5im8rSnoszNyn2c6UeyKrans4X/EMjupgCsx4Z/uHa43gGZixP12crH7sRI5YwbrG184i LhZ+4o3f3GAwxnonHoj/rFc98MKs8PM= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=none; spf=pass (imf30.hostedemail.com: domain of cmarinas@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=cmarinas@kernel.org; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none) ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724343125; a=rsa-sha256; cv=none; b=Uan+XPK9B7jtOUqpYKs9LKFfRHE9RI/dl6VvE0HDEYSfhh+l+kXZWWPXtRYrb8RVnIb0Tr 8Dy7xmEOSPSrqDRK3rOvg8UY2iJFD8FCmtMcsU0zT7v9xmEX/Rr2t+1y+slfNdf/zTyrmO DOg8fV5qYgN+80eIbb+DNEBtIe0qUdI= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 05D0ACE1020; Thu, 22 Aug 2024 16:12:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A751C4AF0C; Thu, 22 Aug 2024 16:12:33 +0000 (UTC) Date: Thu, 22 Aug 2024 17:12:30 +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 , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , Kees Cook , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Florian Weimer , Christian Brauner , Thiago Jung Bauermann , Ross Burton , Yury Khrustalev , Wilco Dijkstra , 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 v11 19/39] arm64/mm: Handle GCS data aborts Message-ID: References: <20240822-arm64-gcs-v11-0-41b81947ecb5@kernel.org> <20240822-arm64-gcs-v11-19-41b81947ecb5@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240822-arm64-gcs-v11-19-41b81947ecb5@kernel.org> X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: A8DE580028 X-Stat-Signature: thk91h3ohb43x18suf9rcepu99xkewof X-HE-Tag: 1724343164-986943 X-HE-Meta: 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 Nrecn793 XRg2OQc/he8WM2FyHM03nS+5FZfAM7BeOrKyMlpPaA27plrPIHk7LH2vAiQqESQdNuptwTpwl/Bof0hHAxQaC5pOarzxQdWL9Xg9Fw3qXCIZDPffqS81GoLY0CEo89H3sg911BBa7vUndryMkx4k1tcD49uG5fCv0Dqo1kCMKjs2ysmIz1qFYcb33DMF3SBC9+UxhZtzPtpLqQG3gIk5exq7eH+yIoK85oNqf13V/DJgaLAly75PWtQhjU/m9muOFa5fxUm06qEqyAIByvhl54TjsdniziSzoObmZfJyX9pTYEOXPV48PwFPs4rc6IRazWfqIvcQd8Vkz63N85mCSzprRnDO9xF0JVWwQs5Jfr/Uy2MXdnBdczC7U6KuPDAMn1OsiDHFqGHmOAcqiFtS3OWA3pSCZ11CxxKCb X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 22, 2024 at 02:15:22AM +0100, Mark Brown wrote: > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 451ba7cbd5ad..3ada31c2ac12 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -486,6 +486,14 @@ static void do_bad_area(unsigned long far, unsigned long esr, > } > } > > +static bool is_gcs_fault(unsigned long esr) > +{ > + if (!esr_is_data_abort(esr)) > + return false; > + > + return ESR_ELx_ISS2(esr) & ESR_ELx_GCS; > +} > + > static bool is_el0_instruction_abort(unsigned long esr) > { > return ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_LOW; > @@ -500,6 +508,23 @@ static bool is_write_abort(unsigned long esr) > return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM); > } > > +static bool is_invalid_gcs_access(struct vm_area_struct *vma, u64 esr) > +{ > + if (!system_supports_gcs()) > + return false; > + > + if (unlikely(is_gcs_fault(esr))) { > + /* GCS accesses must be performed on a GCS page */ > + if (!(vma->vm_flags & VM_SHADOW_STACK)) > + return true; This first check covers the GCSPOPM/RET etc. permission faults on non-GCS vmas. It looks correct. > + } else if (unlikely(vma->vm_flags & VM_SHADOW_STACK)) { > + /* Only GCS operations can write to a GCS page */ > + return is_write_abort(esr); > + } I don't think that's right. The ESR on this path may not even indicate a data abort and ESR.WnR bit check wouldn't make sense. I presume we want to avoid an infinite loop on a (writeable) GCS page when the user does a normal STR but the CPU raises a permission fault. I think this function needs to just return false if !esr_is_data_abort(). > + > + return false; > +} > + > static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > struct pt_regs *regs) > { > @@ -535,6 +560,14 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > /* It was exec fault */ > vm_flags = VM_EXEC; > mm_flags |= FAULT_FLAG_INSTRUCTION; > + } else if (is_gcs_fault(esr)) { > + /* > + * The GCS permission on a page implies both read and > + * write so always handle any GCS fault as a write fault, > + * we need to trigger CoW even for GCS reads. > + */ > + vm_flags = VM_WRITE; > + mm_flags |= FAULT_FLAG_WRITE; > } else if (is_write_abort(esr)) { > /* It was write fault */ > vm_flags = VM_WRITE; > @@ -568,6 +601,13 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, > if (!vma) > goto lock_mmap; > > + if (is_invalid_gcs_access(vma, esr)) { > + vma_end_read(vma); > + fault = 0; > + si_code = SEGV_ACCERR; > + goto bad_area; > + } Here there's a risk that the above function returns true for some unrelated fault that happens to have bit 6 in ESR set. -- Catalin