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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0AFBDC3526C for ; Fri, 18 Dec 2020 22:03:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7C1E23B97 for ; Fri, 18 Dec 2020 22:03:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726351AbgLRWDq (ORCPT ); Fri, 18 Dec 2020 17:03:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:36190 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726347AbgLRWDq (ORCPT ); Fri, 18 Dec 2020 17:03:46 -0500 Date: Fri, 18 Dec 2020 14:03:29 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608329010; bh=ah5TPYDRLqIHq32JpImdGs7kOi1DMjEaUHb3vestQn4=; h=From:To:Subject:In-Reply-To:From; b=C8vc3oa8lfU1zrLZXYK5CMS4oiuWizZ4w9BcitB5pJv4y/JgA36o2+8xUvNtzhfhq pnXRWfmboSHBRo+Rw2V2lt4RVpx1HGtpQkN5mo9onSrEfJTpExkT8qp2NxIAgozsgm NML7B1h2vQlbXveX9ZJ8S53VoJvGEGbXBRS9bfYU= From: Andrew Morton To: akpm@linux-foundation.org, andreyknvl@google.com, aryabinin@virtuozzo.com, Branislav.Rankov@arm.com, catalin.marinas@arm.com, dvyukov@google.com, elver@google.com, eugenis@google.com, glider@google.com, gor@linux.ibm.com, kevin.brodsky@arm.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, vincenzo.frascino@arm.com, will.deacon@arm.com Subject: [patch 38/78] arm64: mte: reset the page tag in page->flags Message-ID: <20201218220329.YlRLmNiSU%akpm@linux-foundation.org> In-Reply-To: <20201218140046.497484741326828e5b5d46ec@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Vincenzo Frascino Subject: arm64: mte: reset the page tag in page->flags The hardware tag-based KASAN for compatibility with the other modes stores the tag associated to a page in page->flags. Due to this the kernel faults on access when it allocates a page with an initial tag and the user changes the tags. Reset the tag associated by the kernel to a page in all the meaningful places to prevent kernel faults on access. Note: An alternative to this approach could be to modify page_to_virt(). This though could end up being racy, in fact if a CPU checks the PG_mte_tagged bit and decides that the page is not tagged but another CPU maps the same with PROT_MTE and becomes tagged the subsequent kernel access would fail. Link: https://lkml.kernel.org/r/9073d4e973747a6f78d5bdd7ebe17f290d087096.1606161801.git.andreyknvl@google.com Signed-off-by: Vincenzo Frascino Signed-off-by: Andrey Konovalov Reviewed-by: Catalin Marinas Tested-by: Vincenzo Frascino Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Branislav Rankov Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Kevin Brodsky Cc: Marco Elver Cc: Vasily Gorbik Cc: Will Deacon Signed-off-by: Andrew Morton --- arch/arm64/kernel/hibernate.c | 5 +++++ arch/arm64/kernel/mte.c | 9 +++++++++ arch/arm64/mm/copypage.c | 9 +++++++++ arch/arm64/mm/mteswap.c | 9 +++++++++ 4 files changed, 32 insertions(+) --- a/arch/arm64/kernel/hibernate.c~arm64-mte-reset-the-page-tag-in-page-flags +++ a/arch/arm64/kernel/hibernate.c @@ -371,6 +371,11 @@ static void swsusp_mte_restore_tags(void unsigned long pfn = xa_state.xa_index; struct page *page = pfn_to_online_page(pfn); + /* + * It is not required to invoke page_kasan_tag_reset(page) + * at this point since the tags stored in page->flags are + * already restored. + */ mte_restore_page_tags(page_address(page), tags); mte_free_tag_storage(tags); --- a/arch/arm64/kernel/mte.c~arm64-mte-reset-the-page-tag-in-page-flags +++ a/arch/arm64/kernel/mte.c @@ -34,6 +34,15 @@ static void mte_sync_page_tags(struct pa return; } + page_kasan_tag_reset(page); + /* + * We need smp_wmb() in between setting the flags and clearing the + * tags because if another thread reads page->flags and builds a + * tagged address out of it, there is an actual dependency to the + * memory access, but on the current thread we do not guarantee that + * the new page->flags are visible before the tags were updated. + */ + smp_wmb(); mte_clear_page_tags(page_address(page)); } --- a/arch/arm64/mm/copypage.c~arm64-mte-reset-the-page-tag-in-page-flags +++ a/arch/arm64/mm/copypage.c @@ -23,6 +23,15 @@ void copy_highpage(struct page *to, stru if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) { set_bit(PG_mte_tagged, &to->flags); + page_kasan_tag_reset(to); + /* + * We need smp_wmb() in between setting the flags and clearing the + * tags because if another thread reads page->flags and builds a + * tagged address out of it, there is an actual dependency to the + * memory access, but on the current thread we do not guarantee that + * the new page->flags are visible before the tags were updated. + */ + smp_wmb(); mte_copy_page_tags(kto, kfrom); } } --- a/arch/arm64/mm/mteswap.c~arm64-mte-reset-the-page-tag-in-page-flags +++ a/arch/arm64/mm/mteswap.c @@ -53,6 +53,15 @@ bool mte_restore_tags(swp_entry_t entry, if (!tags) return false; + page_kasan_tag_reset(page); + /* + * We need smp_wmb() in between setting the flags and clearing the + * tags because if another thread reads page->flags and builds a + * tagged address out of it, there is an actual dependency to the + * memory access, but on the current thread we do not guarantee that + * the new page->flags are visible before the tags were updated. + */ + smp_wmb(); mte_restore_page_tags(page_address(page), tags); return true; _