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

Kang, Luwei
2018-12-28T07:58:06Z

> -----Original Message-----
> From: Gustavo A. R. Silva [mailto:gustavo@embeddedor.com]
> Sent: Thursday, December 27, 2018 4:41 AM
> To: Kang, Luwei <luwei.kang@intel.com>; Paolo Bonzini <pbonzini@redhat.com>; Radim Krčmář <rkrcmar@redhat.com>; Thomas Gleixner
> <tglx@linutronix.de>; Ingo Molnar <mingo@redhat.com>; Borislav Petkov <bp@alien8.de>; H. Peter Anvin <hpa@zytor.com>;
> x86@kernel.org
> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org; Gustavo A. R. Silva <gustavo@embeddedor.com>
> Subject: [PATCH][next] KVM: x86: Fix bit shifting in update_intel_pt_cfg
>
> 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>
> ---
> 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));
> }

Looks good to me, thanks.

Reviewed-by: Luwei Kang <luwei.kang@intel.com>

>
> static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
> --
> 2.20.1