diff mbox series

[4.9,046/116] KVM: x86: Protect kvm_lapic_reg_write() from Spectre-v1/L1TF attacks

Message ID 20200213151900.866636406@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Feb. 13, 2020, 3:19 p.m. UTC 
From: Marios Pomonis <pomonis@google.com>

commit 4bf79cb089f6b1c6c632492c0271054ce52ad766 upstream.

This fixes a Spectre-v1/L1TF vulnerability in kvm_lapic_reg_write().
This function contains index computations based on the
(attacker-controlled) MSR number.

Fixes: 0105d1a52640 ("KVM: x2apic interface to lapic")

Signed-off-by: Nick Finco <nifi@google.com>
Signed-off-by: Marios Pomonis <pomonis@google.com>
Reviewed-by: Andrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kvm/lapic.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)
diff mbox series

Patch

--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -28,6 +28,7 @@ 
 #include <linux/export.h>
 #include <linux/math64.h>
 #include <linux/slab.h>
+#include <linux/nospec.h>
 #include <asm/processor.h>
 #include <asm/msr.h>
 #include <asm/page.h>
@@ -1587,15 +1588,20 @@  int kvm_lapic_reg_write(struct kvm_lapic
 	case APIC_LVTTHMR:
 	case APIC_LVTPC:
 	case APIC_LVT1:
-	case APIC_LVTERR:
+	case APIC_LVTERR: {
 		/* TODO: Check vector */
+		size_t size;
+		u32 index;
+
 		if (!kvm_apic_sw_enabled(apic))
 			val |= APIC_LVT_MASKED;
-
-		val &= apic_lvt_mask[(reg - APIC_LVTT) >> 4];
+		size = ARRAY_SIZE(apic_lvt_mask);
+		index = array_index_nospec(
+				(reg - APIC_LVTT) >> 4, size);
+		val &= apic_lvt_mask[index];
 		kvm_lapic_set_reg(apic, reg, val);
-
 		break;
+	}
 
 	case APIC_LVTT:
 		if (!kvm_apic_sw_enabled(apic))