[PATCH 5.15 198/201] KVM: x86: fix typo in __try_cmpxchg_user causing non-atomicness

Greg Kroah-Hartman
2022-07-27T17:25:36Z

From: Maxim Levitsky <mlevitsk@redhat.com>

commit 33fbe6befa622c082f7d417896832856814bdde0 upstream.

This shows up as a TDP MMU leak when running nested. Non-working cmpxchg on L0
relies makes L1 install two different shadow pages under same spte, and one of
them is leaked.

Fixes: 1c2361f667f36 ("KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220512101420.306759-1-mlevitsk@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/x86.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6933,7 +6933,7 @@ static int emulator_cmpxchg_emulated(str
goto emul_write;

hva = kvm_vcpu_gfn_to_hva(vcpu, gpa_to_gfn(gpa));
- if (kvm_is_error_hva(addr))
+ if (kvm_is_error_hva(hva))
goto emul_write;

hva += offset_in_page(gpa);