From: Marios Pomonis <pomonis@google.com>
Date: Wed, 11 Dec 2019 20:47:43 +0000 (-0800)
Subject: KVM: x86: Refactor picdev_write() to prevent Spectre-v1/L1TF attacks
X-Git-Tag: v3.16.84~23
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6356cde8b18ae7eb06a93d001e996168fce3efce;p=thirdparty%2Fkernel%2Fstable.git

KVM: x86: Refactor picdev_write() to prevent Spectre-v1/L1TF attacks

commit 14e32321f3606e4b0970200b6e5e47ee6f1e6410 upstream.

This fixes a Spectre-v1/L1TF vulnerability in picdev_write().
It replaces index computations based on the (attacked-controlled) port
number with constants through a minor refactoring.

Fixes: 85f455f7ddbe ("KVM: Add support for in-kernel PIC emulation")

Signed-off-by: Nick Finco <nifi@google.com>
Signed-off-by: Marios Pomonis <pomonis@google.com>
Reviewed-by: Andrew Honig <ahonig@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 3.16: pic_{,un}lock() are called outside the switch]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index cc31f7c06d3dd..08b2ad1df9f83 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -486,9 +486,11 @@ static int picdev_write(struct kvm_pic *s,
 	switch (addr) {
 	case 0x20:
 	case 0x21:
+		pic_ioport_write(&s->pics[0], addr, data);
+		break;
 	case 0xa0:
 	case 0xa1:
-		pic_ioport_write(&s->pics[addr >> 7], addr, data);
+		pic_ioport_write(&s->pics[1], addr, data);
 		break;
 	case 0x4d0:
 	case 0x4d1: