[PATCH 5.14 124/125] KVM: SEV-ES: fix another issue with string I/O VMGEXITs

From: Greg Kroah-Hartman
Date: Mon Nov 01 2021 - 05:52:16 EST


From: Paolo Bonzini <pbonzini@xxxxxxxxxx>

commit 9b0971ca7fc75daca80c0bb6c02e96059daea90a upstream.

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@xxxxxxxxxxxxxxx
Fixes: 7ed9abfe8e9f ("KVM: SVM: Support string IO operations for an SEV-ES guest")
Reported-by: Marc Orr <marcorr@xxxxxxxxxx>
Tested-by: Marc Orr <marcorr@xxxxxxxxxx>
Reviewed-by: Marc Orr <marcorr@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/svm/sev.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2592,11 +2592,20 @@ int sev_handle_vmgexit(struct kvm_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)