From: Sean Christopherson seanjc@google.com
[ Upstream commit 0e75225dfa4c5d5d51291f54a3d2d5895bad38da ]
Use BIT_ULL() instead of an open-coded shift to check whether or not a function is enabled in L1's VMFUNC bitmap. This is a benign bug as KVM supports only bit 0, and will fail VM-Enter if any other bits are set, i.e. bits 63:32 are guaranteed to be zero.
Note, "function" is bounded by hardware as VMFUNC will #UD before taking a VM-Exit if the function is greater than 63.
Before: if ((vmcs12->vm_function_control & (1 << function)) == 0) 0x000000000001a916 <+118>: mov $0x1,%eax 0x000000000001a91b <+123>: shl %cl,%eax 0x000000000001a91d <+125>: cltq 0x000000000001a91f <+127>: and 0x128(%rbx),%rax
After: if (!(vmcs12->vm_function_control & BIT_ULL(function & 63))) 0x000000000001a955 <+117>: mov 0x128(%rbx),%rdx 0x000000000001a95c <+124>: bt %rax,%rdx
Fixes: 27c42a1bb867 ("KVM: nVMX: Enable VMFUNC for the L1 hypervisor") Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20210609234235.1244004-3-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/vmx/nested.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index eca3db08d183..d3774d79916d 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -5524,7 +5524,7 @@ static int handle_vmfunc(struct kvm_vcpu *vcpu) }
vmcs12 = get_vmcs12(vcpu); - if ((vmcs12->vm_function_control & (1 << function)) == 0) + if (!(vmcs12->vm_function_control & BIT_ULL(function))) goto fail;
switch (function) {