[PATCH 5.5 235/367] KVM: x86: Protect ioapic_read_indirect() from Spectre-v1/L1TF attacks

Greg Kroah-Hartman
2020-02-10T12:59:24Z

From: Marios Pomonis <pomonis@google.com>

commit 8c86405f606ca8508b8d9280680166ca26723695 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/ioapic.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

--- 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_indirec
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 :