From nobody Sun Feb 8 12:43:00 2026 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 4D750EB64D7 for ; Fri, 16 Jun 2023 19:18:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346130AbjFPTSd (ORCPT ); Fri, 16 Jun 2023 15:18:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345969AbjFPTRF (ORCPT ); Fri, 16 Jun 2023 15:17:05 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9FB23AAD; Fri, 16 Jun 2023 12:17:02 -0700 (PDT) Date: Fri, 16 Jun 2023 19:17:01 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1686943021; h=from:from:sender:sender:reply-to: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:content-transfer-encoding; bh=mYO0hKfedHNGFqZfWJso1Onm/0bxHDH/0cTlv+XOHrU=; b=KxwxzC0SwmizY/4miXjhP+0y2N6G20xyLbBmRp+KDfLCdgaewniyRy7AFF3AGLN0msXZy7 fnqvCZ1IS1Sx7z9utMZOHSDgitkPFLXdPZxZUf+EXJh3mVuDpEdIScaJiD0po7e2MIlc66 7dV6q31sU+ve06yq3B7gqsv8VO5OTDRmeeMmjIaMRuiOMxOqrFM8KuQDVtBH8k3U+hQ/ms RMN4iUPcH/MjlJWmVGXCbct1B95lVlCOoKUMzKGIy67e/KkQkKmh2KUN/+qwNBra8ablp4 Zi69YfdK5YUEjD3C4105bP7ggZC5kIst4Im+vS8LyJbj8AFcWjhpqCR6FCzXrQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1686943021; h=from:from:sender:sender:reply-to: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:content-transfer-encoding; bh=mYO0hKfedHNGFqZfWJso1Onm/0bxHDH/0cTlv+XOHrU=; b=ZlxCU2HFEqiVwJzx5hpmOBAgiL5pZkOuIP7ujseOUjnkE7pgY6G4pM5zTVljaiUIKABWyz iscEPTeOTI79jgCw== From: "tip-bot2 for Rick Edgecombe" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/shstk] mm: Warn on shadow stack memory in wrong vma Cc: Rick Edgecombe , Dave Hansen , Mark Brown , "Mike Rapoport (IBM)" , Pengfei Xu , John Allen , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <168694302101.404.9675949949281395759.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/shstk branch of tip: Commit-ID: aa47900443851e9185db5af6ea197f9a1506c7d3 Gitweb: https://git.kernel.org/tip/aa47900443851e9185db5af6ea197f9a1= 506c7d3 Author: Rick Edgecombe AuthorDate: Mon, 12 Jun 2023 17:10:43 -07:00 Committer: Dave Hansen CommitterDate: Thu, 15 Jun 2023 16:31:33 -07:00 mm: Warn on shadow stack memory in wrong vma The x86 Control-flow Enforcement Technology (CET) feature includes a new type of memory called shadow stack. This shadow stack memory has some unusual properties, which requires some core mm changes to function properly. One sharp edge is that PTEs that are both Write=3D0 and Dirty=3D1 are treated as shadow by the CPU, but this combination used to be created by the kernel on x86. Previous patches have changed the kernel to now avoid creating these PTEs unless they are for shadow stack memory. In case any missed corners of the kernel are still creating PTEs like this for non-shadow stack memory, and to catch any re-introductions of the logic, warn if any shadow stack PTEs (Write=3D0, Dirty=3D1) are found in non-shadow stack VMAs when they are being zapped. This won't catch transient cases but should have decent coverage. In order to check if a PTE is shadow stack in core mm code, add two arch breakouts arch_check_zapped_pte/pmd(). This will allow shadow stack specific code to be kept in arch/x86. Only do the check if shadow stack is supported by the CPU and configured because in rare cases older CPUs may write Dirty=3D1 to a Write=3D0 CPU on older CPUs. This check is handled in pte_shstk()/pmd_shstk(). Signed-off-by: Rick Edgecombe Signed-off-by: Dave Hansen Reviewed-by: Mark Brown Acked-by: Mike Rapoport (IBM) Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook Link: https://lore.kernel.org/all/20230613001108.3040476-18-rick.p.edgecomb= e%40intel.com --- arch/x86/include/asm/pgtable.h | 6 ++++++ arch/x86/mm/pgtable.c | 20 ++++++++++++++++++++ include/linux/pgtable.h | 14 ++++++++++++++ mm/huge_memory.c | 1 + mm/memory.c | 1 + 5 files changed, 42 insertions(+) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 707de18..3fbddf6 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1664,6 +1664,12 @@ static inline bool arch_has_hw_pte_young(void) return true; } =20 +#define arch_check_zapped_pte arch_check_zapped_pte +void arch_check_zapped_pte(struct vm_area_struct *vma, pte_t pte); + +#define arch_check_zapped_pmd arch_check_zapped_pmd +void arch_check_zapped_pmd(struct vm_area_struct *vma, pmd_t pmd); + #ifdef CONFIG_XEN_PV #define arch_has_hw_nonleaf_pmd_young arch_has_hw_nonleaf_pmd_young static inline bool arch_has_hw_nonleaf_pmd_young(void) diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 0ad2c62..101e721 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -894,3 +894,23 @@ pmd_t pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vm= a) =20 return pmd_clear_saveddirty(pmd); } + +void arch_check_zapped_pte(struct vm_area_struct *vma, pte_t pte) +{ + /* + * Hardware before shadow stack can (rarely) set Dirty=3D1 + * on a Write=3D0 PTE. So the below condition + * only indicates a software bug when shadow stack is + * supported by the HW. This checking is covered in + * pte_shstk(). + */ + VM_WARN_ON_ONCE(!(vma->vm_flags & VM_SHADOW_STACK) && + pte_shstk(pte)); +} + +void arch_check_zapped_pmd(struct vm_area_struct *vma, pmd_t pmd) +{ + /* See note in arch_check_zapped_pte() */ + VM_WARN_ON_ONCE(!(vma->vm_flags & VM_SHADOW_STACK) && + pmd_shstk(pmd)); +} diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index f5077a0..c2e9248 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -291,6 +291,20 @@ static inline bool arch_has_hw_pte_young(void) } #endif =20 +#ifndef arch_check_zapped_pte +static inline void arch_check_zapped_pte(struct vm_area_struct *vma, + pte_t pte) +{ +} +#endif + +#ifndef arch_check_zapped_pmd +static inline void arch_check_zapped_pmd(struct vm_area_struct *vma, + pmd_t pmd) +{ +} +#endif + #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long address, diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 37dd56b..c3cc20c 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1681,6 +1681,7 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_ar= ea_struct *vma, */ orig_pmd =3D pmdp_huge_get_and_clear_full(vma, addr, pmd, tlb->fullmm); + arch_check_zapped_pmd(vma, orig_pmd); tlb_remove_pmd_tlb_entry(tlb, pmd, addr); if (vma_is_special_huge(vma)) { if (arch_needs_pgtable_deposit()) diff --git a/mm/memory.c b/mm/memory.c index c1b6fe9..40c0b23 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1412,6 +1412,7 @@ again: continue; ptent =3D ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); + arch_check_zapped_pte(vma, ptent); tlb_remove_tlb_entry(tlb, pte, addr); zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);