[PATCH] KVM: x86: fix a typo in __try_cmpxchg_user that caused cmpxchg to be not atomic

Maxim Levitsky
2022-05-12T10:14:47Z

Fixes: 1c2361f667f36 ("KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/x86.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Yes, this is the root cause of the TDP mmu leak I was doing debug of in the last week.
Non working cmpxchg on which TDP mmu relies makes it install two differnt shadow pages
under same spte.

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8ee8c91fa7625..79cabd3d97d22 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7329,7 +7329,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
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);
--
2.26.3