From patchwork Thu Mar 10 14:18:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 550378 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 7893BC35294 for ; Thu, 10 Mar 2022 14:33:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243827AbiCJOeX (ORCPT ); Thu, 10 Mar 2022 09:34:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51166 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344054AbiCJObj (ORCPT ); Thu, 10 Mar 2022 09:31:39 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CBEB4EC5F4; Thu, 10 Mar 2022 06:29:44 -0800 (PST) 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 ams.source.kernel.org (Postfix) with ESMTPS id 700F6B82544; Thu, 10 Mar 2022 14:29:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BE642C340E8; Thu, 10 Mar 2022 14:29:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646922583; bh=jyBDepQzs3J3bAr8lcobZCUKcw7lYEkUHhe0ftiGO0I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S3ZCoexj2KuGVncK+QPE5ujD2BRknMhaUOqwaH6Xf/nvxYrodHPjZv1rh/BxArSvb 7T7+jx+RDpYzfWg+no/qPy3lfmRpIuyz33i+3A4W9nc4Zr9Xbxm5P1AOFGp46v9YCL JaTUf6Vu9eYloMkyW8cOwSPCX7lQ919DL3D5LqCk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kim Phillips , Borislav Petkov Subject: [PATCH 5.15 07/58] x86/speculation: Use generic retpoline by default on AMD Date: Thu, 10 Mar 2022 15:18:56 +0100 Message-Id: <20220310140813.197314711@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220310140812.983088611@linuxfoundation.org> References: <20220310140812.983088611@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Kim Phillips commit 244d00b5dd4755f8df892c86cab35fb2cfd4f14b upstream. AMD retpoline may be susceptible to speculation. The speculation execution window for an incorrect indirect branch prediction using LFENCE/JMP sequence may potentially be large enough to allow exploitation using Spectre V2. By default, don't use retpoline,lfence on AMD. Instead, use the generic retpoline. Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/bugs.c | 9 --------- 1 file changed, 9 deletions(-) --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -941,15 +941,6 @@ static enum spectre_v2_mitigation __init return SPECTRE_V2_NONE; } - if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || - boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) { - if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) { - pr_err("LFENCE not serializing, switching to generic retpoline\n"); - return SPECTRE_V2_RETPOLINE; - } - return SPECTRE_V2_LFENCE; - } - return SPECTRE_V2_RETPOLINE; }