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 BFCB7C43334 for ; Tue, 12 Jul 2022 18:53:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234688AbiGLSxn (ORCPT ); Tue, 12 Jul 2022 14:53:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56170 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234678AbiGLSxA (ORCPT ); Tue, 12 Jul 2022 14:53:00 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED830DAB8E; Tue, 12 Jul 2022 11:45:18 -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 0195F60AC3; Tue, 12 Jul 2022 18:45:08 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DB83C3411C; Tue, 12 Jul 2022 18:45:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657651507; bh=7NjT53egA3ATlJ9aTxXrE1cWTZ5hf+G2pbGremAuhQQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Cf5ST7QP9zB7ZJVxyQlbCFxoypOPC4eDtjQ3QpnCBApyVwAO24QqSFG1NPzbIZmdc GPB9lknqaq3OaBpaz4b5eIC2b1k1zReBZkkvBdyfnHDSQTdSqJxMthi0FnJ8h+PIcA zveqKnhG6la6MpJdIp/LVs8ALQXlToviqYTyLnN8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexandre Chartre , "Peter Zijlstra (Intel)" , Borislav Petkov , Josh Poimboeuf , Thadeu Lima de Souza Cascardo , Ben Hutchings Subject: [PATCH 5.10 097/130] x86/bugs: Add AMD retbleed= boot parameter Date: Tue, 12 Jul 2022 20:39:03 +0200 Message-Id: <20220712183250.941778542@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220712183246.394947160@linuxfoundation.org> References: <20220712183246.394947160@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: Alexandre Chartre commit 7fbf47c7ce50b38a64576b150e7011ae73d54669 upstream. Add the "retbleed=" boot parameter to select a mitigation for RETBleed. Possible values are "off", "auto" and "unret" (JMP2RET mitigation). The default value is "auto". Currently, "retbleed=auto" will select the unret mitigation on AMD and Hygon and no mitigation on Intel (JMP2RET is not effective on Intel). [peterz: rebase; add hygon] [jpoimboe: cleanups] Signed-off-by: Alexandre Chartre Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- Documentation/admin-guide/kernel-parameters.txt | 15 +++ arch/x86/Kconfig | 3 arch/x86/kernel/cpu/bugs.c | 108 +++++++++++++++++++++++- 3 files changed, 125 insertions(+), 1 deletion(-) --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4656,6 +4656,21 @@ retain_initrd [RAM] Keep initrd memory after extraction + retbleed= [X86] Control mitigation of RETBleed (Arbitrary + Speculative Code Execution with Return Instructions) + vulnerability. + + off - unconditionally disable + auto - automatically select a migitation + unret - force enable untrained return thunks, + only effective on AMD Zen {1,2} + based systems. + + Selecting 'auto' will choose a mitigation method at run + time according to the CPU. + + Not specifying this option is equivalent to retbleed=auto. + rfkill.default_state= 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, etc. communication is blocked by default. --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -465,6 +465,9 @@ config RETPOLINE config CC_HAS_SLS def_bool $(cc-option,-mharden-sls=all) +config CC_HAS_RETURN_THUNK + def_bool $(cc-option,-mfunction-return=thunk-extern) + config SLS bool "Mitigate Straight-Line-Speculation" depends on CC_HAS_SLS && X86_64 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -37,6 +37,7 @@ #include "cpu.h" static void __init spectre_v1_select_mitigation(void); +static void __init retbleed_select_mitigation(void); static void __init spectre_v2_select_mitigation(void); static void __init ssb_select_mitigation(void); static void __init l1tf_select_mitigation(void); @@ -112,6 +113,12 @@ void __init check_bugs(void) /* Select the proper CPU mitigations before patching alternatives: */ spectre_v1_select_mitigation(); + retbleed_select_mitigation(); + /* + * spectre_v2_select_mitigation() relies on the state set by + * retbleed_select_mitigation(); specifically the STIBP selection is + * forced for UNRET. + */ spectre_v2_select_mitigation(); ssb_select_mitigation(); l1tf_select_mitigation(); @@ -709,6 +716,100 @@ static int __init nospectre_v1_cmdline(c early_param("nospectre_v1", nospectre_v1_cmdline); #undef pr_fmt +#define pr_fmt(fmt) "RETBleed: " fmt + +enum retbleed_mitigation { + RETBLEED_MITIGATION_NONE, + RETBLEED_MITIGATION_UNRET, +}; + +enum retbleed_mitigation_cmd { + RETBLEED_CMD_OFF, + RETBLEED_CMD_AUTO, + RETBLEED_CMD_UNRET, +}; + +const char * const retbleed_strings[] = { + [RETBLEED_MITIGATION_NONE] = "Vulnerable", + [RETBLEED_MITIGATION_UNRET] = "Mitigation: untrained return thunk", +}; + +static enum retbleed_mitigation retbleed_mitigation __ro_after_init = + RETBLEED_MITIGATION_NONE; +static enum retbleed_mitigation_cmd retbleed_cmd __ro_after_init = + RETBLEED_CMD_AUTO; + +static int __init retbleed_parse_cmdline(char *str) +{ + if (!str) + return -EINVAL; + + if (!strcmp(str, "off")) + retbleed_cmd = RETBLEED_CMD_OFF; + else if (!strcmp(str, "auto")) + retbleed_cmd = RETBLEED_CMD_AUTO; + else if (!strcmp(str, "unret")) + retbleed_cmd = RETBLEED_CMD_UNRET; + else + pr_err("Unknown retbleed option (%s). Defaulting to 'auto'\n", str); + + return 0; +} +early_param("retbleed", retbleed_parse_cmdline); + +#define RETBLEED_UNTRAIN_MSG "WARNING: BTB untrained return thunk mitigation is only effective on AMD/Hygon!\n" +#define RETBLEED_COMPILER_MSG "WARNING: kernel not compiled with RETPOLINE or -mfunction-return capable compiler!\n" + +static void __init retbleed_select_mitigation(void) +{ + if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) + return; + + switch (retbleed_cmd) { + case RETBLEED_CMD_OFF: + return; + + case RETBLEED_CMD_UNRET: + retbleed_mitigation = RETBLEED_MITIGATION_UNRET; + break; + + case RETBLEED_CMD_AUTO: + default: + if (!boot_cpu_has_bug(X86_BUG_RETBLEED)) + break; + + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) + retbleed_mitigation = RETBLEED_MITIGATION_UNRET; + break; + } + + switch (retbleed_mitigation) { + case RETBLEED_MITIGATION_UNRET: + + if (!IS_ENABLED(CONFIG_RETPOLINE) || + !IS_ENABLED(CONFIG_CC_HAS_RETURN_THUNK)) { + pr_err(RETBLEED_COMPILER_MSG); + retbleed_mitigation = RETBLEED_MITIGATION_NONE; + break; + } + + setup_force_cpu_cap(X86_FEATURE_RETHUNK); + setup_force_cpu_cap(X86_FEATURE_UNRET); + + if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && + boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) + pr_err(RETBLEED_UNTRAIN_MSG); + break; + + default: + break; + } + + pr_info("%s\n", retbleed_strings[retbleed_mitigation]); +} + +#undef pr_fmt #define pr_fmt(fmt) "Spectre V2 : " fmt static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init = @@ -1919,7 +2020,12 @@ static ssize_t srbds_show_state(char *bu static ssize_t retbleed_show_state(char *buf) { - return sprintf(buf, "Vulnerable\n"); + if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET && + (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && + boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)) + return sprintf(buf, "Vulnerable: untrained return thunk on non-Zen uarch\n"); + + return sprintf(buf, "%s\n", retbleed_strings[retbleed_mitigation]); } static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,