From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AF97217F3 for ; Mon, 31 Oct 2022 07:02:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02AF0C433D6; Mon, 31 Oct 2022 07:02:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1667199752; bh=07W7zI9iEbaiXk7gc5MAnpK7zhFbpqP+oao+OP9d1j8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GnOvUr0MMmRkmm26pl9OjeUAZfhDXMdEIcj4MnoghZ28Mt0CGTqfAYk8YMqGSo9ZK 9Cgw4R1BC8eD8zz0IVg2Cfxjbrxs0bYI46ZwOZXBjpdEq1ZNjoNH6z3RJQSak5T9XA Nc7Frq/my3VRJ0pDRYMxA2b8BNckPxvg2dMTxz4E= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexandre Chartre , "Peter Zijlstra (Intel)" , Borislav Petkov , Josh Poimboeuf , Thadeu Lima de Souza Cascardo , Suraj Jitindar Singh Subject: [PATCH 4.14 10/34] x86/bugs: Add AMD retbleed= boot parameter Date: Mon, 31 Oct 2022 08:02:43 +0100 Message-Id: <20221031070140.354732901@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221031070140.108124105@linuxfoundation.org> References: <20221031070140.108124105@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 [ bp: Adjust context - no jmp2ret mitigation exists ] Signed-off-by: Suraj Jitindar Singh Signed-off-by: Greg Kroah-Hartman --- Documentation/admin-guide/kernel-parameters.txt | 12 ++++ arch/x86/kernel/cpu/bugs.c | 70 +++++++++++++++++++++++- 2 files changed, 81 insertions(+), 1 deletion(-) --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3965,6 +3965,18 @@ 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 + + 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/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -36,6 +36,7 @@ #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); @@ -111,6 +112,12 @@ 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(); @@ -706,6 +713,67 @@ 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 +}; + +enum retbleed_mitigation_cmd { + RETBLEED_CMD_OFF, + RETBLEED_CMD_AUTO +}; + +const char * const retbleed_strings[] = { + [RETBLEED_MITIGATION_NONE] = "Vulnerable" +}; + +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 + pr_err("Unknown retbleed option (%s). Defaulting to 'auto'\n", str); + + return 0; +} +early_param("retbleed", retbleed_parse_cmdline); + +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_AUTO: + default: + if (!boot_cpu_has_bug(X86_BUG_RETBLEED)) + break; + break; + } + + switch (retbleed_mitigation) { + 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 = @@ -1901,7 +1969,7 @@ static ssize_t srbds_show_state(char *bu static ssize_t retbleed_show_state(char *buf) { - return sprintf(buf, "Vulnerable\n"); + return sprintf(buf, "%s\n", retbleed_strings[retbleed_mitigation]); } static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,