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From f3b9db45027a40369fe13c4661c4249d1df8c8d0 Mon Sep 17 00:00:00 2001
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From: Andrew Honig <ahonig@google.com>
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Date: Wed, 18 Nov 2015 14:50:23 -0800
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Subject: [PATCH] KVM: x86: Reload pit counters for all channels when restoring
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state
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Currently if userspace restores the pit counters with a count of 0
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on channels 1 or 2 and the guest attempts to read the count on those
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channels, then KVM will perform a mod of 0 and crash. This will ensure
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that 0 values are converted to 65536 as per the spec.
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This is CVE-2015-7513.
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Signed-off-by: Andy Honig <ahonig@google.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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[Backported to 4.3.y by Josh Boyer <jwboyer@fedoraproject.org>]
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---
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arch/x86/kvm/x86.c | 9 ++++++---
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1 file changed, 6 insertions(+), 3 deletions(-)
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
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index 43609af03283..e124f9c8391e 100644
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--- a/arch/x86/kvm/x86.c
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+++ b/arch/x86/kvm/x86.c
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@@ -3437,10 +3437,11 @@ static int kvm_vm_ioctl_get_pit(struct kvm *kvm, struct kvm_pit_state *ps)
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static int kvm_vm_ioctl_set_pit(struct kvm *kvm, struct kvm_pit_state *ps)
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{
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int r = 0;
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-
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+ int i;
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mutex_lock(&kvm->arch.vpit->pit_state.lock);
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memcpy(&kvm->arch.vpit->pit_state, ps, sizeof(struct kvm_pit_state));
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- kvm_pit_load_count(kvm, 0, ps->channels[0].count, 0);
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+ for (i = 0; i < 3; i++)
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+ kvm_pit_load_count(kvm, i, ps->channels[i].count, 0);
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mutex_unlock(&kvm->arch.vpit->pit_state.lock);
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return r;
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}
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@@ -3461,6 +3462,7 @@ static int kvm_vm_ioctl_get_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
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static int kvm_vm_ioctl_set_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
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{
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int r = 0, start = 0;
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+ int i;
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u32 prev_legacy, cur_legacy;
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mutex_lock(&kvm->arch.vpit->pit_state.lock);
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prev_legacy = kvm->arch.vpit->pit_state.flags & KVM_PIT_FLAGS_HPET_LEGACY;
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@@ -3470,7 +3472,8 @@ static int kvm_vm_ioctl_set_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
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memcpy(&kvm->arch.vpit->pit_state.channels, &ps->channels,
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sizeof(kvm->arch.vpit->pit_state.channels));
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kvm->arch.vpit->pit_state.flags = ps->flags;
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- kvm_pit_load_count(kvm, 0, kvm->arch.vpit->pit_state.channels[0].count, start);
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+ for (i = 0; i < 3; i++)
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+ kvm_pit_load_count(kvm, i, kvm->arch.vpit->pit_state.channels[i].count, start);
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mutex_unlock(&kvm->arch.vpit->pit_state.lock);
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return r;
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}
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--
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2.5.0
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