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 6EDA7C433FE for ; Tue, 15 Nov 2022 00:47:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237344AbiKOArW (ORCPT ); Mon, 14 Nov 2022 19:47:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231293AbiKOArU (ORCPT ); Mon, 14 Nov 2022 19:47:20 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 06E051DA44 for ; Mon, 14 Nov 2022 16:47:20 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B5565B810FA for ; Tue, 15 Nov 2022 00:47:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 509F7C433D7; Tue, 15 Nov 2022 00:47:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1668473237; bh=ZWEex2GMUFVDhV7QZupl+4as6Yj6HfA+7hPSuAngs2Y=; h=Date:To:From:Subject:From; b=Tl3vV50LzzYMl81MNg56DOlyNaZF5BAm+/dw8i926FzTGGDc//e8zmP9Hp601ri0r 4p+5slroJsKC69JnPBpVvnCLAEReylpDUy3R1zwTc1yY6i2qX0wyQXSvRST/lotbt+ BmV45d1A19v6AERC2UNbYtftOEPhkwN10pqO2vas= Date: Mon, 14 Nov 2022 16:47:16 -0800 To: mm-commits@vger.kernel.org, rppt@linux.vnet.ibm.com, nadav.amit@gmail.com, axelrasmussen@google.com, apopple@nvidia.com, aarcange@redhat.com, peterx@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: + mm-uffd-sanity-check-write-bit-for-uffd-wp-protected-ptes.patch added to mm-unstable branch Message-Id: <20221115004717.509F7C433D7@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The patch titled Subject: mm/uffd: sanity check write bit for uffd-wp protected ptes has been added to the -mm mm-unstable branch. Its filename is mm-uffd-sanity-check-write-bit-for-uffd-wp-protected-ptes.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-uffd-sanity-check-write-bit-for-uffd-wp-protected-ptes.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Peter Xu Subject: mm/uffd: sanity check write bit for uffd-wp protected ptes Date: Sun, 13 Nov 2022 19:04:47 -0500 Let's add one sanity check for CONFIG_DEBUG_VM on the write bit in whatever chance we have when walking through the pgtables. It can bring the error earlier even before the app notices the data was corrupted on the snapshot. Also it helps us to identify this is a wrong pgtable setup, so hopefully a great information to have for debugging too. Link: https://lkml.kernel.org/r/20221114000447.1681003-3-peterx@redhat.com Signed-off-by: Peter Xu Cc: Andrea Arcangeli Cc: Alistair Popple Cc: Axel Rasmussen Cc: Mike Rapoport Cc: Nadav Amit Signed-off-by: Andrew Morton --- arch/x86/include/asm/pgtable.h | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/pgtable.h~mm-uffd-sanity-check-write-bit-for-uffd-wp-protected-ptes +++ a/arch/x86/include/asm/pgtable.h @@ -291,7 +291,23 @@ static inline pte_t pte_clear_flags(pte_ #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP static inline int pte_uffd_wp(pte_t pte) { - return pte_flags(pte) & _PAGE_UFFD_WP; + bool wp = pte_flags(pte) & _PAGE_UFFD_WP; + +#ifdef CONFIG_DEBUG_VM + /* + * Having write bit for wr-protect-marked present ptes is fatal, + * because it means the uffd-wp bit will be ignored and write will + * just go through. + * + * Use any chance of pgtable walking to verify this (e.g., when + * page swapped out or being migrated for all purposes). It means + * something is already wrong. Tell the admin even before the + * process crashes. We also nail it with wrong pgtable setup. + */ + WARN_ON_ONCE(wp && pte_write(pte)); +#endif + + return wp; } static inline pte_t pte_mkuffd_wp(pte_t pte) _ Patches currently in -mm which might be from peterx@redhat.com are mm-migrate-fix-read-only-page-got-writable-when-recover-pte.patch mm-always-compile-in-pte-markers.patch mm-use-pte-markers-for-swap-errors.patch mm-uffd-sanity-check-write-bit-for-uffd-wp-protected-ptes.patch