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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C30C7C43334 for ; Tue, 14 Jun 2022 18:41:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345403AbiFNSll (ORCPT ); Tue, 14 Jun 2022 14:41:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58118 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356426AbiFNSlS (ORCPT ); Tue, 14 Jun 2022 14:41:18 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6DD054969A; Tue, 14 Jun 2022 11:41:16 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id DD414617C2; Tue, 14 Jun 2022 18:41:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3B55C3411B; Tue, 14 Jun 2022 18:41:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655232075; bh=+PS1FasQL1d9Ko84VEhMcUiqKJHZX1Lc9ZLC323IQNw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iCPw61Ufk2mlJwOaGufwWL/lSuuIJzUOqcETeDEQmzLDv1bobLcdt2HVepQmqVD5p WpcqjBbGtbQjn3D9VOqEVG9Fna91SKz392o5Es7EP21D/phfZ8VgHO4blNwu9snvjk gTLvhIj6gmiHQiClaQtUFSzvJeiDi6vOedQQlYPw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Pawan Gupta , Thomas Gleixner , Josh Poimboeuf , Borislav Petkov , Thadeu Lima de Souza Cascardo Subject: [PATCH 4.9 15/20] x86/speculation/mmio: Enable CPU Fill buffer clearing on idle Date: Tue, 14 Jun 2022 20:39:58 +0200 Message-Id: <20220614183725.698486215@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220614183722.061550591@linuxfoundation.org> References: <20220614183722.061550591@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Pawan Gupta commit 99a83db5a605137424e1efe29dc0573d6a5b6316 upstream When the CPU is affected by Processor MMIO Stale Data vulnerabilities, Fill Buffer Stale Data Propagator (FBSDP) can propagate stale data out of Fill buffer to uncore buffer when CPU goes idle. Stale data can then be exploited with other variants using MMIO operations. Mitigate it by clearing the Fill buffer before entering idle state. Signed-off-by: Pawan Gupta Signed-off-by: Thomas Gleixner Co-developed-by: Josh Poimboeuf Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/bugs.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -416,6 +416,14 @@ static void __init mmio_select_mitigatio static_branch_enable(&mmio_stale_data_clear); /* + * If Processor-MMIO-Stale-Data bug is present and Fill Buffer data can + * be propagated to uncore buffers, clearing the Fill buffers on idle + * is required irrespective of SMT state. + */ + if (!(ia32_cap & ARCH_CAP_FBSDP_NO)) + static_branch_enable(&mds_idle_clear); + + /* * Check if the system has the right microcode. * * CPU Fill buffer clear mitigation is enumerated by either an explicit @@ -1181,6 +1189,8 @@ static void update_indir_branch_cond(voi /* Update the static key controlling the MDS CPU buffer clear in idle */ static void update_mds_branch_idle(void) { + u64 ia32_cap = x86_read_arch_cap_msr(); + /* * Enable the idle clearing if SMT is active on CPUs which are * affected only by MSBDS and not any other MDS variant. @@ -1192,10 +1202,12 @@ static void update_mds_branch_idle(void) if (!boot_cpu_has_bug(X86_BUG_MSBDS_ONLY)) return; - if (sched_smt_active()) + if (sched_smt_active()) { static_branch_enable(&mds_idle_clear); - else + } else if (mmio_mitigation == MMIO_MITIGATION_OFF || + (ia32_cap & ARCH_CAP_FBSDP_NO)) { static_branch_disable(&mds_idle_clear); + } } #define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"