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X-CSE-ConnectionGUID: H3K0BbsDSa6QSVkxfDWgAQ== X-CSE-MsgGUID: YSGaKy4bSVq/9I6c6aWjrA== X-IronPort-AV: E=McAfee;i="6700,10204,11222"; a="53823113" X-IronPort-AV: E=Sophos;i="6.11,199,1725346800"; d="scan'208";a="53823113" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2024 07:51:40 -0800 X-CSE-ConnectionGUID: 4mfraGhKRCmt/bynR9/rsw== X-CSE-MsgGUID: PfkoazUeQAyLWwyn2mejBA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,148,1728975600"; d="scan'208";a="87655334" Received: from jairdeje-mobl1.amr.corp.intel.com (HELO [10.124.220.61]) ([10.124.220.61]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2024 07:51:39 -0800 Message-ID: <1c1015f8-1a47-4e5b-b088-f83054d2f613@intel.com> Date: Tue, 12 Nov 2024 07:51:38 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC][PATCH] x86/cpu/bugs: Consider having old Intel microcode to be a vulnerability To: Alex Murray , dave.hansen@linux.intel.com Cc: bp@alien8.de, linux-kernel@vger.kernel.org, tglx@linutronix.de, x86@kernel.org References: <87v7wtvty0.fsf@canonical.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/11/24 22:37, Alex Murray wrote: >> == Microcode Revision Discussion == >> >> The microcode versions in the table were generated from the Intel >> microcode git repo: >> >> 29f82f7429c ("microcode-20241029 Release") > > This upstream microcode release only contained an update for a > functional issue[1] - not any fixes for security issues. So it would not > really be correct to say a machine running the previous microcode > revision is vulnerable. There are literally two things this patch "says". One is in userspace and can be literally read as: /sys/devices/system/cpu/vulnerabilities/old_microcode "You are vulnerable to old CPU microcode". The other is in the code: X86_BUG_OLD_MICROCODE. Which can literally be read to say "you have a CPU bug called 'old microcode'. (Oh, and I guess this comes out in /proc/cpuinfo too). If you think this is confusing, we can document our way out of it or revise the changelog. But we kinda get to define what the file and the X86_BUG mean in the first place. I don't really see how it's possible to argue that they're "incorrect". > As such, should the table of microcode revisions only be generated > from the upstream microcode releases that contain fixes for security > issues? No, I don't think so. First, I honestly don't want to have this discussion every three months where folks can argue about whether a given microcode release is functional or security. Or, even worse, which individual microcode *image* is which. Second, running kernels with functional issues is *BAD*. As a kernel policy, we don't want users running with old microcode. Security bugs only hurt our users but functional bugs hurt the kernel too because users blame the kernel when they hit them and kernel developers spend time chasing those issues down. So I guess it boils down to: First, should we tell users when their microcode is old? If so, how should we do it?