Commit d23d33ea authored by Borislav Petkov's avatar Borislav Petkov Committed by Thomas Gleixner
Browse files

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: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20220525161232.14924-4-bp@alien8.de
parent a77a94f8

arch/x86/kernel/cpu/microcode/core.c

+5 −0
Original line number Original line Diff line number Diff line
@@ -493,6 +493,9 @@ static int microcode_reload_late(void) 
{

{

	int ret;

	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_in,  0);

	atomic_set(&late_cpus_out, 0);

	atomic_set(&late_cpus_out, 0);
@@ -541,6 +544,8 @@ static ssize_t reload_store(struct device *dev, 
	if (ret == 0)

	if (ret == 0)

		ret = size;

		ret = size;





	add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);



	return ret;

	return ret;

}

}