From: Sean Christopherson <seanjc@google.com>
Date: Wed, 9 Jun 2021 16:42:22 -0700
Subject: KVM: nVMX: Ensure 64-bit shift when checking VMFUNC bitmap
Git-commit: 0e75225dfa4c5d5d51291f54a3d2d5895bad38da
Patch-mainline: v5.14-rc1
References: bsc#1188774
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: Jose R. Ziviani <jziviani@suse.de>
---
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 14093234438f..f3f4cc7f8e09 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5121,7 +5121,7 @@ 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) {
--
2.32.0