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

BugLink: https://bugs.launchpad.net/bugs/1863588
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>
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>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index d859ae8890d0a6d144427cff8e36fa18078c715a..77b4fe151726c5bdd7c9459725b29a7ebbc6a966 100644 (file)
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -291,6 +291,7 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
 
                if (index >= IOAPIC_NUM_PINS)
                        return;
+               index = array_index_nospec(index, IOAPIC_NUM_PINS);
                e = &ioapic->redirtbl[index];
                mask_before = e->fields.mask;
                /* Preserve read-only fields */