From nobody Fri Dec 19 00:03:33 2025 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 92C5FC5479D for ; Mon, 9 Jan 2023 05:28:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230398AbjAIF2m (ORCPT ); Mon, 9 Jan 2023 00:28:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230352AbjAIF22 (ORCPT ); Mon, 9 Jan 2023 00:28:28 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3823F2C6 for ; Sun, 8 Jan 2023 21:28:27 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C2F151042; Sun, 8 Jan 2023 21:29:08 -0800 (PST) Received: from a077893.blr.arm.com (unknown [10.162.40.15]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 5923C3F71A; Sun, 8 Jan 2023 21:28:24 -0800 (PST) From: Anshuman Khandual To: linux-arm-kernel@lists.infradead.org, will@kernel.org, catalin.marinas@arm.com Cc: Anshuman Khandual , Mark Rutland , Andrew Morton , linux-kernel@vger.kernel.org Subject: [PATCH V2] arm64/mm: Intercept pfn changes in set_pte_at() Date: Mon, 9 Jan 2023 10:58:16 +0530 Message-Id: <20230109052816.405335-1-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Changing pfn on a user page table mapped entry, without first going through break-before-make (BBM) procedure is unsafe. This just updates set_pte_at() to intercept such changes, via an updated pgattr_change_is_safe(). This new check happens via __check_racy_pte_update(), which has now been renamed as __check_safe_pte_update(). Cc: Catalin Marinas Cc: Will Deacon Cc: Mark Rutland Cc: Andrew Morton Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual Acked-by: Mark Rutland --- This applies on v6.2-rc3. This patch had some test time on an internal CI system without any issues being reported. Changes in V1: https://lore.kernel.org/all/20221116031001.292236-1-anshuman.khandual@arm.c= om/ arch/arm64/include/asm/pgtable.h | 8 ++++++-- arch/arm64/mm/mmu.c | 8 +++++++- 2 files changed, 13 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgta= ble.h index b4bbeed80fb6..832c9c8fb58f 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -275,6 +275,7 @@ static inline void set_pte(pte_t *ptep, pte_t pte) } =20 extern void __sync_icache_dcache(pte_t pteval); +bool pgattr_change_is_safe(u64 old, u64 new); =20 /* * PTE bits configuration in the presence of hardware Dirty Bit Management @@ -292,7 +293,7 @@ extern void __sync_icache_dcache(pte_t pteval); * PTE_DIRTY || (PTE_WRITE && !PTE_RDONLY) */ =20 -static inline void __check_racy_pte_update(struct mm_struct *mm, pte_t *pt= ep, +static inline void __check_safe_pte_update(struct mm_struct *mm, pte_t *pt= ep, pte_t pte) { pte_t old_pte; @@ -318,6 +319,9 @@ static inline void __check_racy_pte_update(struct mm_st= ruct *mm, pte_t *ptep, VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte), "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx", __func__, pte_val(old_pte), pte_val(pte)); + VM_WARN_ONCE(!pgattr_change_is_safe(pte_val(old_pte), pte_val(pte)), + "%s: unsafe attribute change: 0x%016llx -> 0x%016llx", + __func__, pte_val(old_pte), pte_val(pte)); } =20 static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr, @@ -346,7 +350,7 @@ static inline void __set_pte_at(struct mm_struct *mm, u= nsigned long addr, mte_sync_tags(old_pte, pte); } =20 - __check_racy_pte_update(mm, ptep, pte); + __check_safe_pte_update(mm, ptep, pte); =20 set_pte(ptep, pte); } diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 14c87e8d69d8..a1d16b35c4f6 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -133,7 +133,7 @@ static phys_addr_t __init early_pgtable_alloc(int shift) return phys; } =20 -static bool pgattr_change_is_safe(u64 old, u64 new) +bool pgattr_change_is_safe(u64 old, u64 new) { /* * The following mapping attributes may be updated in live @@ -145,6 +145,12 @@ static bool pgattr_change_is_safe(u64 old, u64 new) if (old =3D=3D 0 || new =3D=3D 0) return true; =20 + /* If old and new ptes are valid, pfn should not change */ + if (pte_valid(__pte(old)) && pte_valid(__pte(new))) { + if (pte_pfn(__pte(old)) !=3D pte_pfn(__pte(new))) + return false; + } + /* live contiguous mappings may not be manipulated at all */ if ((old | new) & PTE_CONT) return false; --=20 2.25.1