From d23d33ea0fcdc4bbb484990bf53867f99c63ccab Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 25 May 2022 18:12:31 +0200 Subject: [PATCH] x86/microcode: Taint and warn on late loading Warn before it is attempted and taint the kernel. Late loading microcode can lead to malfunction of the kernel when the microcode update changes behaviour. There is no way for the kernel to determine whether its safe or not. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20220525161232.14924-4-bp@alien8.de --- arch/x86/kernel/cpu/microcode/core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index c717db6b6856..801b44ac3851 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -493,6 +493,9 @@ static int microcode_reload_late(void) { int ret; + pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n"); + pr_err("You should switch to early loading, if possible.\n"); + atomic_set(&late_cpus_in, 0); atomic_set(&late_cpus_out, 0); @@ -541,6 +544,8 @@ put: if (ret == 0) ret = size; + add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + return ret; }