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 27D81C433FE for ; Wed, 9 Mar 2022 16:09:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233258AbiCIQKf (ORCPT ); Wed, 9 Mar 2022 11:10:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44350 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234458AbiCIQHg (ORCPT ); Wed, 9 Mar 2022 11:07:36 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB068144F40; Wed, 9 Mar 2022 08:03:43 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 54F0861666; Wed, 9 Mar 2022 16:03:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6034EC340E8; Wed, 9 Mar 2022 16:03:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646841818; bh=rSTOUX5LUvBCX6WBogDAqooyuvYNrP66hsRf3uWRExc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ACdvPAL4piYXHwUHvqfvsT+KvEHyNLzi70achmGqFwwtR0XlsN3ZLKcGjKQRisbKO UVbfEAevPTe5g/5hUHxp+plQkemtI3hpsOHsobgDWKxZ4Je7rNrySzFER1uC2OTQLs ARZmCzAIFBWkGjdJGvMqTHLGi9Z/lcUwmQMcIv6k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kim Phillips , Borislav Petkov Subject: [PATCH 4.19 07/18] x86/speculation: Use generic retpoline by default on AMD Date: Wed, 9 Mar 2022 16:59:44 +0100 Message-Id: <20220309155856.375338710@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220309155856.155540075@linuxfoundation.org> References: <20220309155856.155540075@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 | 8 -------- 1 file changed, 8 deletions(-) --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -898,14 +898,6 @@ static enum spectre_v2_mitigation __init return SPECTRE_V2_NONE; } - if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { - 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; }