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 3ABFBC433EF for ; Wed, 20 Jul 2022 01:12:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240278AbiGTBMT (ORCPT ); Tue, 19 Jul 2022 21:12:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33830 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240749AbiGTBLy (ORCPT ); Tue, 19 Jul 2022 21:11:54 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1E84052DDE; Tue, 19 Jul 2022 18:11:37 -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 ams.source.kernel.org (Postfix) with ESMTPS id D3E09B81DD6; Wed, 20 Jul 2022 01:11:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 55332C341C6; Wed, 20 Jul 2022 01:11:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658279494; bh=jO5Qr1reqLeMFicoZVt0cDGgKhNXpWcoW54RfQB8xLI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EBb59WtINn6XVykC9zQXA3QgRym7lzyfo39FECddWquhQtR2N8Ea80S2qu/sU1XmD cvJm4UHE6/a5+kQcbQDOXhpLlCp+R/dAu2wkXTR1BvWRfKz+k9ffOMIq6AmL9J8PV/ myG41lUjM3scm8pofwNsrk0HEzC4Wv+K8Mu6ArO9YVZdLOZw3DtmsKrruDDs/bSQv+ jYHW7gtHbjB6D/3p1NbPaXuSfY50vjDYUvvLNAFWt0hbcKq+PmZVGMEJRTFwdncKy9 Nqlgs69Ysp1CrkXhz0X2ouzvXEt07JGFUaH3P2BBa6s6QLWdHISLQd00nqz9Moowgv AloDyBr59XwUA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kim Phillips , Josh Poimboeuf , Peter Zijlstra , Borislav Petkov , Sasha Levin , corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, paulmck@kernel.org, akpm@linux-foundation.org, keescook@chromium.org, rdunlap@infradead.org, damien.lemoal@opensource.wdc.com, jpoimboe@kernel.org, pawan.kumar.gupta@linux.intel.com, alexandre.chartre@oracle.com, sblbir@amazon.com, linux-doc@vger.kernel.org Subject: [PATCH AUTOSEL 5.18 15/54] x86/bugs: Enable STIBP for JMP2RET Date: Tue, 19 Jul 2022 21:09:52 -0400 Message-Id: <20220720011031.1023305-15-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220720011031.1023305-1-sashal@kernel.org> References: <20220720011031.1023305-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kim Phillips [ Upstream commit e8ec1b6e08a2102d8755ccb06fa26d540f26a2fa ] For untrained return thunks to be fully effective, STIBP must be enabled or SMT disabled. Co-developed-by: Josh Poimboeuf Signed-off-by: Josh Poimboeuf Signed-off-by: Kim Phillips Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Signed-off-by: Sasha Levin --- .../admin-guide/kernel-parameters.txt | 16 +++-- arch/x86/kernel/cpu/bugs.c | 58 +++++++++++++++---- 2 files changed, 57 insertions(+), 17 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 1af5341eb233..7631757db799 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5128,11 +5128,17 @@ 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. + off - no mitigation + auto - automatically select a migitation + auto,nosmt - automatically select a mitigation, + disabling SMT if necessary for + the full mitigation (only on Zen1 + and older without STIBP). + unret - force enable untrained return thunks, + only effective on AMD f15h-f17h + based systems. + unret,nosmt - like unret, will disable SMT when STIBP + is not available. Selecting 'auto' will choose a mitigation method at run time according to the CPU. diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 5fdf031fd694..50a2c813c347 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -776,19 +776,34 @@ static enum retbleed_mitigation retbleed_mitigation __ro_after_init = static enum retbleed_mitigation_cmd retbleed_cmd __ro_after_init = RETBLEED_CMD_AUTO; +static int __ro_after_init retbleed_nosmt = false; + 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); + while (str) { + char *next = strchr(str, ','); + if (next) { + *next = 0; + next++; + } + + 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 if (!strcmp(str, "nosmt")) { + retbleed_nosmt = true; + } else { + pr_err("Ignoring unknown retbleed option (%s).", str); + } + + str = next; + } return 0; } @@ -834,6 +849,10 @@ static void __init retbleed_select_mitigation(void) setup_force_cpu_cap(X86_FEATURE_RETHUNK); setup_force_cpu_cap(X86_FEATURE_UNRET); + if (!boot_cpu_has(X86_FEATURE_STIBP) && + (retbleed_nosmt || cpu_mitigations_auto_nosmt())) + cpu_smt_disable(false); + if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) pr_err(RETBLEED_UNTRAIN_MSG); @@ -1080,6 +1099,13 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) mode = SPECTRE_V2_USER_STRICT_PREFERRED; + if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) { + if (mode != SPECTRE_V2_USER_STRICT && + mode != SPECTRE_V2_USER_STRICT_PREFERRED) + pr_info("Selecting STIBP always-on mode to complement retbleed mitigation'\n"); + mode = SPECTRE_V2_USER_STRICT_PREFERRED; + } + spectre_v2_user_stibp = mode; set_mode: @@ -2090,10 +2116,18 @@ static ssize_t srbds_show_state(char *buf) static ssize_t retbleed_show_state(char *buf) { - 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"); + if (retbleed_mitigation == RETBLEED_MITIGATION_UNRET) { + if (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; SMT %s\n", + retbleed_strings[retbleed_mitigation], + !sched_smt_active() ? "disabled" : + spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT || + spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT_PREFERRED ? + "enabled with STIBP protection" : "vulnerable"); + } return sprintf(buf, "%s\n", retbleed_strings[retbleed_mitigation]); } -- 2.35.1