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 21F55C433FE for ; Wed, 9 Mar 2022 16:13:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235050AbiCIQOv (ORCPT ); Wed, 9 Mar 2022 11:14:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41372 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234848AbiCIQIK (ORCPT ); Wed, 9 Mar 2022 11:08:10 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90155182BD4; Wed, 9 Mar 2022 08:04:33 -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 2ECFAB82220; Wed, 9 Mar 2022 16:04:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8122AC340E8; Wed, 9 Mar 2022 16:04:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646841871; bh=Dpe0tk9GNdSgB2qTr+VBTPTKFcv/dNvPbCSODMJpdas=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OStw1tfxUhOhJzbt9MKcWvRXdeunziDYOmeajiRsMBxywYXhIKHiQQWp8pywB6i01 g5CsLEy0rZtdNx1+ovbNbHxXgKwODVaybIs6fDLbdcPZAxfYpXZjSh/iFHy8KX2PMA DgT3qk1W2uFJQUss95n/GNcJlEE/RiO7UOF6zvG8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kim Phillips , Borislav Petkov Subject: [PATCH 5.4 07/18] x86/speculation: Use generic retpoline by default on AMD Date: Wed, 9 Mar 2022 16:59:56 +0100 Message-Id: <20220309155856.770328357@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220309155856.552503355@linuxfoundation.org> References: <20220309155856.552503355@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: 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 @@ -898,15 +898,6 @@ 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; }