From nobody Sun Feb 8 18:44:44 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 239E0C6FD1D for ; Mon, 20 Mar 2023 16:49:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232137AbjCTQtA (ORCPT ); Mon, 20 Mar 2023 12:49:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231925AbjCTQrl (ORCPT ); Mon, 20 Mar 2023 12:47:41 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3AEC9360B9; Mon, 20 Mar 2023 09:41:12 -0700 (PDT) Date: Mon, 20 Mar 2023 16:39:24 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1679330364; 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=mMq0WQr0hq8wDvTsZ+f3hHbrwqrKiCvC+eM50M6jNR8=; b=ljZlztWfPAfQ7tQ801qIxZdeaSaUIzjH7U/e3GKtaRKxUT+rGN4CDImQ2b91lDwMYvonmr fvIDMdXB6hRuEkullqBSeTNOTEsVXAHDxMvgnz/Kn0SuDK7qcmBEnng+QilCeTKLNhlcg2 IfEWn16q6dFYMZ+snMRfXEu4pxM4c/e8V0NsjAaG1C2+xmClhhQPBSkQnRXVaym2Trh1/Q /HJ0QMcSRVWYxm3UHEgO6N1Tl8q92d3LqYRRmvXqE/W2P00UvNIuoawh0bP3I+7zpvo5SM 39UDsIg1Cms0zwo0KNqxX/Ltun/UDJvFyetnVXEdBXK46kjBG9yFVD3k3SYpEA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1679330364; 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=mMq0WQr0hq8wDvTsZ+f3hHbrwqrKiCvC+eM50M6jNR8=; b=RwQ6Ayjsd0HkKvNIRJWbV1zcDgVUoJ/5tg21LJx3z1sQ1EAtVLRCn019BO7dHCmXTSiw2q 9TsRokrfMDobemDg== 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] x86/mm: Warn if create Write=0,Dirty=1 with raw prot Cc: Rick Edgecombe , Dave Hansen , "Borislav Petkov (AMD)" , "Mike Rapoport (IBM)" , Pengfei Xu , John Allen , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <167933036405.5837.15340188207531246966.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: 6ad563c4b42f64038456f838f3bd712acc95cbcb Gitweb: https://git.kernel.org/tip/6ad563c4b42f64038456f838f3bd712ac= c95cbcb Author: Rick Edgecombe AuthorDate: Sat, 18 Mar 2023 17:15:22 -07:00 Committer: Dave Hansen CommitterDate: Mon, 20 Mar 2023 09:01:11 -07:00 x86/mm: Warn if create Write=3D0,Dirty=3D1 with raw prot When user shadow stack is in use, Write=3D0,Dirty=3D1 is treated by the CPU= as shadow stack memory. So for shadow stack memory this bit combination is valid, but when Dirty=3D1,Write=3D1 (conventionally writable) memory is bei= ng write protected, the kernel has been taught to transition the Dirty=3D1 bit to SavedDirty=3D1, to avoid inadvertently creating shadow stack memory. It does this inside pte_wrprotect() because it knows the PTE is not intended to be a writable shadow stack entry, it is supposed to be write protected. However, when a PTE is created by a raw prot using mk_pte(), mk_pte() can't know whether to adjust Dirty=3D1 to SavedDirty=3D1. It can't distinguish between the caller intending to create a shadow stack PTE or needing the SavedDirty shift. The kernel has been updated to not do this, and so Write=3D0,Dirty=3D1 memory should only be created by the pte_mkfoo() helpers. Add a warning to make sure no new mk_pte() start doing this, like, for example, set_memory_rox() did. Signed-off-by: Rick Edgecombe Signed-off-by: Dave Hansen Reviewed-by: Borislav Petkov (AMD) Acked-by: Mike Rapoport (IBM) Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook Link: https://lore.kernel.org/all/20230319001535.23210-28-rick.p.edgecombe%= 40intel.com --- arch/x86/include/asm/pgtable.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index e5b3dce..7142f99 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1032,7 +1032,15 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd) * (Currently stuck as a macro because of indirect forward reference * to linux/mm.h:page_to_nid()) */ -#define mk_pte(page, pgprot) pfn_pte(page_to_pfn(page), (pgprot)) +#define mk_pte(page, pgprot) \ +({ \ + pgprot_t __pgprot =3D pgprot; \ + \ + WARN_ON_ONCE(cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && \ + (pgprot_val(__pgprot) & (_PAGE_DIRTY | _PAGE_RW)) =3D=3D \ + _PAGE_DIRTY); \ + pfn_pte(page_to_pfn(page), __pgprot); \ +}) =20 static inline int pmd_bad(pmd_t pmd) {