Re: [PATCH][next] KVM: x86: Fix bit shifting in update_intel_pt_cfg

Wei Yang
2018-12-27T03:35:45Z

On Wed, Dec 26, 2018 at 02:40:59PM -0600, Gustavo A. R. Silva wrote:
>ctl_bitmask in pt_desc is of type u64. When an integer like 0xf is
>being left shifted more than 32 bits, the behavior is undefined.
>
>Fix this by adding suffix ULL to integer 0xf.
>
>Addresses-Coverity-ID: 1476095 ("Bad bit shift operation")
>Fixes: 6c0f0bba85a0 ("KVM: x86: Introduce a function to initialize the PT configuration")
>Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Looks good.

Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>

>---
> arch/x86/kvm/vmx/vmx.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>index cbd55e7aeae5..251c68a74bbe 100644
>--- a/arch/x86/kvm/vmx/vmx.c
>+++ b/arch/x86/kvm/vmx/vmx.c
>@@ -7012,7 +7012,7 @@ static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
>
> /* unmask address range configure area */
> for (i = 0; i < vmx->pt_desc.addr_range; i++)
>- vmx->pt_desc.ctl_bitmask &= ~(0xf << (32 + i * 4));
>+ vmx->pt_desc.ctl_bitmask &= ~(0xfULL << (32 + i * 4));
> }
>
> static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
>--
>2.20.1

--
Wei Yang
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