From: Marios Pomonis <pomonis@google.com>
Date: Wed, 11 Dec 2019 20:47:45 +0000 (-0800)
Subject: KVM: x86: Protect ioapic_write_indirect() from Spectre-v1/L1TF attacks
X-Git-Tag: v3.16.84~21
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=56b51e25ffb93ae142652400c35ea43f0899d0c2;p=thirdparty%2Fkernel%2Fstable.git

KVM: x86: Protect ioapic_write_indirect() from Spectre-v1/L1TF attacks

commit 670564559ca35b439c8d8861fc399451ddf95137 upstream.

This fixes a Spectre-v1/L1TF vulnerability in ioapic_write_indirect().
This function contains index computations based on the
(attacker-controlled) IOREGSEL register.

This patch depends on patch
"KVM: x86: Protect ioapic_read_indirect() from Spectre-v1/L1TF attacks".

Fixes: 70f93dae32ac ("KVM: Use temporary variable to shorten lines.")

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: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index c022e959dd887..456131c04c903 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -312,6 +312,7 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
 		ioapic_debug("change redir index %x val %x\n", index, val);
 		if (index >= IOAPIC_NUM_PINS)
 			return;
+		index = array_index_nospec(index, IOAPIC_NUM_PINS);
 		e = &ioapic->redirtbl[index];
 		mask_before = e->fields.mask;
 		if (ioapic->ioregsel & 1) {