[PATCH] x86/microcode/intel: Clear patch pointer before jettisoning the initrd

[Borislav Petkov]

From: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>

During early boot, load_ucode_intel_ap() uses __load_ucode_intel()
to obtain a pointer to the relevant microcode patch (embedded in the
initrd), and stores this value in intel_ucode_patch to speed up the
microcode patch application for subsequent CPUs.

On resuming from suspend-to-RAM, however, load_ucode_ap() calls
load_ucode_intel_ap() for each non-boot-CPU. By then the initramfs is
long gone so the pointer stored in intel_ucode_patch no longer points to
a valid microcode patch.

Clear that pointer so that we effectively fallback to the CPU hotplug
notifier callbacks to update the microcode.

Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.10..
[ Edit and massage commit message. ]
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/kernel/cpu/microcode/intel.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index afdfd237b59f..f522415bf9e5 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -619,6 +619,9 @@ int __init save_microcode_in_initrd_intel(void)
 
 	show_saved_mc();
 
+	/* initrd is going away, clear patch ptr. */
+	intel_ucode_patch = NULL;
+
 	return 0;
 }
 
-- 
2.13.0