[PATCH v2 04/13] KVM: x86: Protect ioapic_read_indirect() from Spectre-v1/L1TF attacks

Marios Pomonis
2019-12-11T20:48:43Z

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

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

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index 9fd2dd89a1c5..0c672eefaabe 100644
--- 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 :
--
2.24.0.525.g8f36a354ae-goog