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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 064F2C04E84 for ; Wed, 15 May 2019 12:06:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B7DC020843 for ; Wed, 15 May 2019 12:06:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557921983; bh=CX3+NgyXHWJ/A5jbSUuIf6vviov4VbQA1rAfKKbRaXY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=BjWcGfBPv4mlCHbFyjXfNyTo1i9jzw/8L22nFnZP9mkOW7Kbl2K2Nep8kxF4Lj8XK HiX0+CtE0+HUdY2mu1ScSOa9+nyV0pGx5PnGw+dcuD7O74IcxO/l2Y2gvBAAx3BcPw m3lwaNCSRotEz/fEG62WYL/5C+6KJQjfwrYCa04M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729782AbfEOMGW (ORCPT ); Wed, 15 May 2019 08:06:22 -0400 Received: from mail.kernel.org ([198.145.29.99]:43880 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729362AbfEOLKK (ORCPT ); Wed, 15 May 2019 07:10:10 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 01F312168B; Wed, 15 May 2019 11:10:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557918609; bh=CX3+NgyXHWJ/A5jbSUuIf6vviov4VbQA1rAfKKbRaXY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wCD+vYCJ8Q/MUyGp7E2c3+W6X3rJEtkzaHruetcDJ3U7xG6HI3zV2HUHz6KCnMMBT iaFItEGXD0MbKrVFHtc1wPBygMACaq8oiYb3milQ0We72/ZfBfMzdykJygMePEPro1 upSPtTwVZdig3ZdXwbD9ZiynErqoYOow/8DuFa+M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Nadav Amit , Thomas Gleixner , "Peter Zijlstra (Intel)" , Dave Hansen , Andi Kleen , Josh Poimboeuf , Michal Hocko , Vlastimil Babka , Sean Christopherson , Andy Lutomirski , Ben Hutchings Subject: [PATCH 4.4 197/266] x86/mm: Use WRITE_ONCE() when setting PTEs Date: Wed, 15 May 2019 12:55:04 +0200 Message-Id: <20190515090729.610153491@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190515090722.696531131@linuxfoundation.org> References: <20190515090722.696531131@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nadav Amit commit 9bc4f28af75a91aea0ae383f50b0a430c4509303 upstream. When page-table entries are set, the compiler might optimize their assignment by using multiple instructions to set the PTE. This might turn into a security hazard if the user somehow manages to use the interim PTE. L1TF does not make our lives easier, making even an interim non-present PTE a security hazard. Using WRITE_ONCE() to set PTEs and friends should prevent this potential security hazard. I skimmed the differences in the binary with and without this patch. The differences are (obviously) greater when CONFIG_PARAVIRT=n as more code optimizations are possible. For better and worse, the impact on the binary with this patch is pretty small. Skimming the code did not cause anything to jump out as a security hazard, but it seems that at least move_soft_dirty_pte() caused set_pte_at() to use multiple writes. Signed-off-by: Nadav Amit Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Cc: Dave Hansen Cc: Andi Kleen Cc: Josh Poimboeuf Cc: Michal Hocko Cc: Vlastimil Babka Cc: Sean Christopherson Cc: Andy Lutomirski Link: https://lkml.kernel.org/r/20180902181451.80520-1-namit@vmware.com [bwh: Backported to 4.4: - Drop changes in pmdp_establish(), native_set_p4d(), pudp_set_access_flags() - Adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/pgtable_64.h | 16 ++++++++-------- arch/x86/mm/pgtable.c | 6 +++--- 2 files changed, 11 insertions(+), 11 deletions(-) --- a/arch/x86/include/asm/pgtable_64.h +++ b/arch/x86/include/asm/pgtable_64.h @@ -44,15 +44,15 @@ struct mm_struct; void set_pte_vaddr_pud(pud_t *pud_page, unsigned long vaddr, pte_t new_pte); -static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr, - pte_t *ptep) +static inline void native_set_pte(pte_t *ptep, pte_t pte) { - *ptep = native_make_pte(0); + WRITE_ONCE(*ptep, pte); } -static inline void native_set_pte(pte_t *ptep, pte_t pte) +static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr, + pte_t *ptep) { - *ptep = pte; + native_set_pte(ptep, native_make_pte(0)); } static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte) @@ -62,7 +62,7 @@ static inline void native_set_pte_atomic static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd) { - *pmdp = pmd; + WRITE_ONCE(*pmdp, pmd); } static inline void native_pmd_clear(pmd_t *pmd) @@ -98,7 +98,7 @@ static inline pmd_t native_pmdp_get_and_ static inline void native_set_pud(pud_t *pudp, pud_t pud) { - *pudp = pud; + WRITE_ONCE(*pudp, pud); } static inline void native_pud_clear(pud_t *pud) @@ -131,7 +131,7 @@ static inline pgd_t *native_get_shadow_p static inline void native_set_pgd(pgd_t *pgdp, pgd_t pgd) { - *pgdp = kaiser_set_shadow_pgd(pgdp, pgd); + WRITE_ONCE(*pgdp, kaiser_set_shadow_pgd(pgdp, pgd)); } static inline void native_pgd_clear(pgd_t *pgd) --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -247,7 +247,7 @@ static void pgd_mop_up_pmds(struct mm_st if (pgd_val(pgd) != 0) { pmd_t *pmd = (pmd_t *)pgd_page_vaddr(pgd); - pgdp[i] = native_make_pgd(0); + pgd_clear(&pgdp[i]); paravirt_release_pmd(pgd_val(pgd) >> PAGE_SHIFT); pmd_free(mm, pmd); @@ -424,7 +424,7 @@ int ptep_set_access_flags(struct vm_area int changed = !pte_same(*ptep, entry); if (changed && dirty) { - *ptep = entry; + set_pte(ptep, entry); pte_update_defer(vma->vm_mm, address, ptep); } @@ -441,7 +441,7 @@ int pmdp_set_access_flags(struct vm_area VM_BUG_ON(address & ~HPAGE_PMD_MASK); if (changed && dirty) { - *pmdp = entry; + set_pmd(pmdp, entry); pmd_update_defer(vma->vm_mm, address, pmdp); /* * We had a write-protection fault here and changed the pmd