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

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

Fixes: a2c118bfab8b ("KVM: Fix bounds checking in ioapic indirect register reads (CVE-2013-1798)")

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>

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index 7312aab..c5776fe 100644 (file)
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -36,6 +36,7 @@
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/export.h>
+#include <linux/nospec.h>
 #include <asm/processor.h>
 #include <asm/page.h>
 #include <asm/current.h>
@@ -68,13 +69,14 @@ static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
        default:
                {
                        u32 redir_index = (ioapic->ioregsel - 0x10) >> 1;
-                       u64 redir_content;
+                       u64 redir_content = ~0ULL;
 
-                       if (redir_index < IOAPIC_NUM_PINS)
-                               redir_content =
-                                       ioapic->redirtbl[redir_index].bits;
-                       else
-                               redir_content = ~0ULL;
+                       if (redir_index < IOAPIC_NUM_PINS) {
+                               u32 index = array_index_nospec(
+                                       redir_index, IOAPIC_NUM_PINS);
+
+                               redir_content = ioapic->redirtbl[index].bits;
+                       }
 
                        result = (ioapic->ioregsel & 0x1) ?
                            (redir_content >> 32) & 0xffffffff :