From nobody Mon Dec 15 11:26:01 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 C3280C001B0 for ; Tue, 8 Aug 2023 20:33:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231458AbjHHUdH (ORCPT ); Tue, 8 Aug 2023 16:33:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234444AbjHHUc3 (ORCPT ); Tue, 8 Aug 2023 16:32:29 -0400 Received: from icts-p-cavuit-1.kulnet.kuleuven.be (icts-p-cavuit-1.kulnet.kuleuven.be [IPv6:2a02:2c40:0:c0::25:132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6A6B65B3 for ; Tue, 8 Aug 2023 12:56:46 -0700 (PDT) X-KULeuven-Envelope-From: jo.vanbulck@cs.kuleuven.be X-KULeuven-Scanned: Found to be clean X-KULeuven-ID: F404F2005A.A3714 X-KULeuven-Information: Katholieke Universiteit Leuven Received: from icts-p-ceifnet-smtps-0.kuleuven.be (icts-p-ceifnet-smtps.service.icts.svcd [IPv6:2a02:2c40:0:51:144:242:ac11:2f]) by icts-p-cavuit-1.kulnet.kuleuven.be (Postfix) with ESMTP id F404F2005A; Tue, 8 Aug 2023 21:56:41 +0200 (CEST) BCmilterd-Mark-Subject: no BCmilterd-Errors: BCmilterd-Report: SA-HVU#DKIM_VALID#0.00,SA-HVU#DKIM_VALID_AU#0.00,SA-HVU#DKIM_SIGNED#0.00 X-CAV-Cluster: smtps DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cs.kuleuven.be; s=cav; t=1691524601; bh=YcH4Fg8CUorp1vXIDgTjg2krAfCLOYoN7h6ArsaNswo=; h=From:To:Cc:Subject:Date; b=Czh0JcdLmMopZXkc9Kcmzs4UT1Kln8gnXzSMQTp5IUm4ZyNNwYYJnGYDwwXyGnbv/ nis0Waq0F1zBXDh7mvZV8YqmdZmC9QBxTOjhR3D7OadboMslO7s8LQG3l5BkMnTcgf 4+qmPugUs3xr0jlMJRxGLN5Ik6kc8oJRrZe0kljE= Received: from localhost.localdomain (rrcs-24-123-120-98.central.biz.rr.com [24.123.120.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by icts-p-ceifnet-smtps-0.kuleuven.be (Postfix) with ESMTPSA id 39D54D4F7B7AA; Tue, 8 Aug 2023 21:56:38 +0200 (CEST) X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Jo Van Bulck To: linux-kernel@vger.kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, mingo@redhat.com Cc: x86@kernel.org, bp@alien8.de, tglx@linutronix.de, hpa@zytor.com, Jo Van Bulck Subject: [PATCH RESEND] x86/pti: Fix kernel warnings for pti= and nopti cmdline options. Date: Tue, 8 Aug 2023 12:56:15 -0700 Message-Id: <20230808195615.9795-1-jo.vanbulck@cs.kuleuven.be> 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" Parse the pti=3D and nopti cmdline options using early_param to fix 'Unknown kernel command line parameters "nopti", will be passed to user space' warnings in the kernel log when nopti or pti=3D are passed to the kernel cmdline on x86 platforms. Additionally allow the kernel to warn for malformed pti=3D options. Signed-off-by: Jo Van Bulck --- Resending this as I haven't heard back yet. I'd be happy to incorporate any feedback. Also adding test output before/after patch for reference: dmesg | grep -e "page tables isolation" -e "Command line" \ -e "Malformed" -e "Unknown kernel command line parameters" \ && cat /sys/devices/system/cpu/vulnerabilities/meltdown Before patch =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D KERNEL_CMDLINE=3D"nopti" [ 0.000000] Command line: root=3D/dev/vda console=3DttyS0 nopti [ 0.009875] Kernel/User page tables isolation: disabled on command line. [ 0.021498] Unknown kernel command line parameters "nopti", will be pas= sed to user space. Vulnerable KERNEL_CMDLINE=3D"pti=3Doff" [ 0.000000] Command line: root=3D/dev/vda console=3DttyS0 pti=3Doff [ 0.009564] Kernel/User page tables isolation: disabled on command line. [ 0.019542] Unknown kernel command line parameters "pti=3Doff", will be= passed to user space. Vulnerable KERNEL_CMDLINE=3D"pti=3Dinvalid" [ 0.000000] Command line: root=3D/dev/vda console=3DttyS0 pti=3Dinvalid [ 0.021409] Unknown kernel command line parameters "pti=3Dinvalid", wil= l be passed to user space. [ 0.022411] Kernel/User page tables isolation: enabled Mitigation: PTI After patch =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D KERNEL_CMDLINE=3D"nopti" [ 0.000000] Command line: root=3D/dev/vda console=3DttyS0 nopti [ 0.009775] Kernel/User page tables isolation: disabled on command line. Vulnerable KERNEL_CMDLINE=3D"pti=3Doff" [ 0.000000] Command line: root=3D/dev/vda console=3DttyS0 pti=3Doff [ 0.009879] Kernel/User page tables isolation: disabled on command line. Vulnerable KERNEL_CMDLINE=3D"pti=3Dinvalid" [ 0.000000] Command line: root=3D/dev/vda console=3DttyS0 pti=3Dinvalid [ 0.000000] Malformed early option 'pti' [ 0.020892] Kernel/User page tables isolation: enabled Mitigation: PTI arch/x86/mm/pti.c | 56 +++++++++++++++++++++++------------------------ 1 file changed, 27 insertions(+), 29 deletions(-) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 78414c6d1..ea5841cf9 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -69,6 +69,7 @@ static void __init pti_print_if_secure(const char *reason) pr_info("%s\n", reason); } =20 +/* Assume mode is auto unless overridden via cmdline below */ static enum pti_mode { PTI_AUTO =3D 0, PTI_FORCE_OFF, @@ -77,50 +78,47 @@ static enum pti_mode { =20 void __init pti_check_boottime_disable(void) { - char arg[5]; - int ret; - - /* Assume mode is auto unless overridden. */ - pti_mode =3D PTI_AUTO; - if (hypervisor_is_type(X86_HYPER_XEN_PV)) { pti_mode =3D PTI_FORCE_OFF; pti_print_if_insecure("disabled on XEN PV."); return; } =20 - ret =3D cmdline_find_option(boot_command_line, "pti", arg, sizeof(arg)); - if (ret > 0) { - if (ret =3D=3D 3 && !strncmp(arg, "off", 3)) { - pti_mode =3D PTI_FORCE_OFF; - pti_print_if_insecure("disabled on command line."); - return; - } - if (ret =3D=3D 2 && !strncmp(arg, "on", 2)) { - pti_mode =3D PTI_FORCE_ON; - pti_print_if_secure("force enabled on command line."); - goto enable; - } - if (ret =3D=3D 4 && !strncmp(arg, "auto", 4)) { - pti_mode =3D PTI_AUTO; - goto autosel; - } - } - - if (cmdline_find_option_bool(boot_command_line, "nopti") || - cpu_mitigations_off()) { + if (pti_mode =3D=3D PTI_FORCE_OFF || cpu_mitigations_off()) { pti_mode =3D PTI_FORCE_OFF; pti_print_if_insecure("disabled on command line."); return; } =20 -autosel: - if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) + if (pti_mode =3D=3D PTI_AUTO && !boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) return; -enable: + + if (pti_mode =3D=3D PTI_FORCE_ON) + pti_print_if_secure("force enabled on command line."); setup_force_cpu_cap(X86_FEATURE_PTI); } =20 +static int __init pti_parse_cmdline(char *arg) +{ + if (!strcmp(arg, "off")) + pti_mode =3D PTI_FORCE_OFF; + else if (!strcmp(arg, "on")) + pti_mode =3D PTI_FORCE_ON; + else if (!strcmp(arg, "auto")) + pti_mode =3D PTI_AUTO; + else + return -EINVAL; + return 0; +} +early_param("pti", pti_parse_cmdline); + +static int __init pti_parse_cmdline_nopti(char *arg) +{ + pti_mode =3D PTI_FORCE_OFF; + return 0; +} +early_param("nopti", pti_parse_cmdline_nopti); + pgd_t __pti_set_user_pgtbl(pgd_t *pgdp, pgd_t pgd) { /* base-commit: 1399419a8db7b3d6083b47062358d95dc8ec9663 --=20 2.25.1