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 c022e959dd887af6f654951d714622d9b1108578..456131c04c90349b72181612b2dffbf1aa5a3515 100644 (file)
--- 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) {