[RFC PATCH -v2] x86/microcode: Taint and warn on late loading
From: Borislav Petkov
Date: Wed May 25 2022 - 08:52:35 EST
On Wed, May 25, 2022 at 12:03:52PM +0200, Peter Zijlstra wrote:
> Should we not warn *before* attempting the ucode update? Should the
> whole thing come unstuck, you at least have some clue.
Sure.
From: Borislav Petkov <bp@xxxxxxx>
Warn before it is attempted and taint the kernel.
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
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 @@ static ssize_t reload_store(struct device *dev,
if (ret == 0)
ret = size;
+ add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+
return ret;
}
--
2.35.1
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette