linux-kernel - [PATCH] x86/its: Warn when microcode is old

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250611-its-warn-v1-1-02eb9a75ce9c@linux.intel.com>
Date: Wed, 11 Jun 2025 17:08:27 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
	Josh Poimboeuf <jpoimboe@...nel.org>
Subject: [PATCH] x86/its: Warn when microcode is old

A microcode update is required for IBPB to be effective against ITS. On
Intel, X86_BUG_OLD_MICROCODE is set already when old microcode is detected.
In such a case system is tainted and a warning is issued.

Also warn that userspace could be vulnerable to ITS.

Suggested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 7f94e6a5497d9a2d312a76095e48d6b364565777..7aa3ae00e6b4daa5e42217b66c50cd46d6bcc115 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1427,6 +1427,10 @@ static void __init its_select_mitigation(void)
 		return;
 	}
 
+	/* For IBPB to be effective against ITS */
+	if (boot_cpu_has_bug(X86_BUG_OLD_MICROCODE))
+		pr_warn("Old microcode, userspace may be vulnerable to ITS\n");
+
 	if (its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF &&
 	    !IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)) {
 		pr_err("RSB stuff mitigation not supported, using default\n");

---
base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
change-id: 20250611-its-warn-b292b10896e3