@@ -167,6 +167,8 @@ static inline u16 apic_logical_id(struct kvm_apic_map *map, u32 ldr)
return ldr & map->lid_mask;
}
+#define KVM_X2APIC_CID_BITS 0
+
static void recalculate_apic_map(struct kvm *kvm)
{
struct kvm_apic_map *new, *old = NULL;
@@ -204,7 +206,8 @@ static void recalculate_apic_map(struct kvm *kvm)
if (apic_x2apic_mode(apic)) {
new->ldr_bits = 32;
new->cid_shift = 16;
- new->cid_mask = new->lid_mask = 0xffff;
+ new->cid_mask = (1 << KVM_X2APIC_CID_BITS) - 1;
+ new->lid_mask = 0xffff;
} else if (kvm_apic_sw_enabled(apic) &&
!new->cid_mask /* flat mode */ &&
kvm_apic_get_reg(apic, APIC_DFR) == APIC_DFR_CLUSTER) {
This is a note to let you know that I have just added a patch titled KVM: x86: fix guest-initiated crash with x2apic (CVE-2013-6376) to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.16. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 7d5d34ca95582f5fc0f59dc30a8e25d1b76bfe50 Mon Sep 17 00:00:00 2001 From: Gleb Natapov <gleb@redhat.com> Date: Thu, 12 Dec 2013 21:20:08 +0100 Subject: KVM: x86: fix guest-initiated crash with x2apic (CVE-2013-6376) commit 17d68b763f09a9ce824ae23eb62c9efc57b69271 upstream. A guest can cause a BUG_ON() leading to a host kernel crash. When the guest writes to the ICR to request an IPI, while in x2apic mode the following things happen, the destination is read from ICR2, which is a register that the guest can control. kvm_irq_delivery_to_apic_fast uses the high 16 bits of ICR2 as the cluster id. A BUG_ON is triggered, which is a protection against accessing map->logical_map with an out-of-bounds access and manages to avoid that anything really unsafe occurs. The logic in the code is correct from real HW point of view. The problem is that KVM supports only one cluster with ID 0 in clustered mode, but the code that has the bug does not take this into account. Reported-by: Lars Bull <larsbull@google.com> Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/x86/kvm/lapic.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) -- 1.8.3.2