x86/KVM: Make sure KVM_VCPU_FLUSH_TLB flag is not missed

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commit b043138246 upstream.

There is a potential race in record_steal_time() between setting
host-local vcpu->arch.st.steal.preempted to zero (i.e. clearing
KVM_VCPU_PREEMPTED) and propagating this value to the guest with
kvm_write_guest_cached(). Between those two events the guest may
still see KVM_VCPU_PREEMPTED in its copy of kvm_steal_time, set
KVM_VCPU_FLUSH_TLB and assume that hypervisor will do the right
thing. Which it won't.

Instad of copying, we should map kvm_steal_time and that will
guarantee atomicity of accesses to @preempted.

This is part of CVE-2019-3016.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Boris Ostrovsky 2019-12-05 03:45:32 +00:00 • committed by Greg Kroah-Hartman

parent f6ad4449dd

commit 91fefc3e32

1 changed files with 30 additions and 21 deletions

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arch/x86/kvm/x86.c

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