If the guest requests string I/O from the hypervisor via VMGEXIT, SW_EXITINFO2 will contain the REP count. However, sev_es_string_io was incorrectly treating it as the size of the GHCB buffer in bytes.

This fixes the "outsw" test in the experimental SEV tests of kvm-unit-tests.

Cc: stable@vger.kernel.org Fixes: 7ed9abfe8e9f ("KVM: SVM: Support string IO operations for an SEV-ES guest") Reported-by: Marc Orr marcorr@google.com Tested-by: Marc Orr marcorr@google.com Reviewed-by: Marc Orr marcorr@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com --- arch/x86/kvm/svm/sev.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index e672493b5d8d..efd207fd335e 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2579,11 +2579,20 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)

int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in) { - if (!setup_vmgexit_scratch(svm, in, svm->vmcb->control.exit_info_2)) + int count; + int bytes; + + if (svm->vmcb->control.exit_info_2 > INT_MAX) + return -EINVAL; + + count = svm->vmcb->control.exit_info_2; + if (unlikely(check_mul_overflow(count, size, &bytes))) + return -EINVAL; + + if (!setup_vmgexit_scratch(svm, in, bytes)) return -EINVAL;

- return kvm_sev_es_string_io(&svm->vcpu, size, port, - svm->ghcb_sa, svm->ghcb_sa_len / size, in); + return kvm_sev_es_string_io(&svm->vcpu, size, port, svm->ghcb_sa, count, in); }

void sev_es_init_vmcb(struct vcpu_svm *svm)