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

[Kang, Luwei]

> -----Original Message-----
> From: Gustavo A. R. Silva [mailto:gustavo@xxxxxxxxxxxxxx]
> Sent: Thursday, December 27, 2018 4:41 AM
> To: Kang, Luwei <luwei.kang@xxxxxxxxx>; Paolo Bonzini <pbonzini@xxxxxxxxxx>; Radim Krčmář <rkrcmar@xxxxxxxxxx>; Thomas Gleixner
> <tglx@xxxxxxxxxxxxx>; Ingo Molnar <mingo@xxxxxxxxxx>; Borislav Petkov <bp@xxxxxxxxx>; H. Peter Anvin <hpa@xxxxxxxxx>;
> x86@xxxxxxxxxx
> Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxxx>
> ---
>  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@xxxxxxxxx>

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