Commit 2ab637df authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Sean Christopherson
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KVM: VMX: hyper-v: Prevent impossible NULL pointer dereference in evmcs_load() 



GCC 12.3.0 complains about a potential NULL pointer dereference in
evmcs_load() as hv_get_vp_assist_page() can return NULL. In fact, this
cannot happen because KVM verifies (hv_init_evmcs()) that every CPU has a
valid VP assist page and aborts enabling the feature otherwise. CPU
onlining path is also checked in vmx_hardware_enable().

To make the compiler happy and to future proof the code, add a KVM_BUG_ON()
sentinel. It doesn't seem to be possible (and logical) to observe
evmcs_load() happening without an active vCPU so it is presumed that
kvm_get_running_vcpu() can't return NULL.

No functional change intended.

Reported-by: default avatarMirsad Todorovac <mtodorovac69@gmail.com>
Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20240816130124.286226-1-vkuznets@redhat.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 41ab0d59

arch/x86/kvm/vmx/vmx_onhyperv.h

+8 −0
Original line number Diff line number Diff line
@@ -104,6 +104,14 @@ static inline void evmcs_load(u64 phys_addr) 
	struct hv_vp_assist_page *vp_ap =

		hv_get_vp_assist_page(smp_processor_id());



	/*

	 * When enabling eVMCS, KVM verifies that every CPU has a valid hv_vp_assist_page()

	 * and aborts enabling the feature otherwise. CPU onlining path is also checked in

	 * vmx_hardware_enable().

	 */

	if (KVM_BUG_ON(!vp_ap, kvm_get_running_vcpu()->kvm))

		return;



	if (current_evmcs->hv_enlightenments_control.nested_flush_hypercall)

		vp_ap->nested_control.features.directhypercall = 1;

	vp_ap->current_nested_vmcs = phys_addr;