110 lines
5.3 KiB
Diff
110 lines
5.3 KiB
Diff
Bugzilla: 1042099
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Thu, 12 Dec 2013 12:37:16 -0800 (PST)
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From: Paolo Bonzini <pbonzini@redhat.com>
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To: linux-kernel@vger.kernel.org
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Cc: gleb@redhat.com, kvm@vger.kernel.org, pmatouse@redhat.com,
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stable@vger.kernel.org
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Subject: [PATCH] KVM: x86: fix guest-initiated crash with x2apic (CVE-2013-6376)
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Date: Thu, 12 Dec 2013 21:36:54 +0100
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Message-Id: <1386880614-23300-4-git-send-email-pbonzini@redhat.com>
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From: Gleb Natapov <gleb@redhat.com>
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A guest can cause a BUG_ON() leading to a host kernel crash.
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When the guest writes to the ICR to request an IPI, while in x2apic
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mode the following things happen, the destination is read from
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ICR2, which is a register that the guest can control.
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kvm_irq_delivery_to_apic_fast uses the high 16 bits of ICR2 as the
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cluster id. A BUG_ON is triggered, which is a protection against
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accessing map->logical_map with an out-of-bounds access and manages
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to avoid that anything really unsafe occurs.
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The logic in the code is correct from real HW point of view. The problem
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is that KVM supports only one cluster with ID 0 in clustered mode, but
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the code that has the bug does not take this into account.
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Reported-by: Lars Bull <larsbull@google.com>
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Cc: stable@vger.kernel.org
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Signed-off-by: Gleb Natapov <gleb@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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---
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arch/x86/kvm/lapic.c | 5 ++++-
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1 file changed, 4 insertions(+), 1 deletion(-)
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diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
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index b8bec45c1610..801dc3fd66e1 100644
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--- a/arch/x86/kvm/lapic.c
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+++ b/arch/x86/kvm/lapic.c
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@@ -143,6 +143,8 @@ static inline int kvm_apic_id(struct kvm_lapic *apic)
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return (kvm_apic_get_reg(apic, APIC_ID) >> 24) & 0xff;
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}
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+#define KMV_X2APIC_CID_BITS 0
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+
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static void recalculate_apic_map(struct kvm *kvm)
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{
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struct kvm_apic_map *new, *old = NULL;
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@@ -180,7 +182,8 @@ static void recalculate_apic_map(struct kvm *kvm)
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if (apic_x2apic_mode(apic)) {
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new->ldr_bits = 32;
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new->cid_shift = 16;
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- new->cid_mask = new->lid_mask = 0xffff;
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+ new->cid_mask = (1 << KMV_X2APIC_CID_BITS) - 1;
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+ new->lid_mask = 0xffff;
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} else if (kvm_apic_sw_enabled(apic) &&
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!new->cid_mask /* flat mode */ &&
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kvm_apic_get_reg(apic, APIC_DFR) == APIC_DFR_CLUSTER) {
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--
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1.8.3.1
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--
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