linux-kernel - RE: [PATCH][next] KVM: x86: Fix bit shifting in update_intel_pt

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Date:   Fri, 28 Dec 2018 07:58:06 +0000
From:   "Kang, Luwei" <luwei.kang@...el.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH][next] KVM: x86: Fix bit shifting in update_intel_pt_cfg



> -----Original Message-----
> From: Gustavo A. R. Silva [mailto:gustavo@...eddedor.com]
> Sent: Thursday, December 27, 2018 4:41 AM
> To: Kang, Luwei <luwei.kang@...el.com>; Paolo Bonzini <pbonzini@...hat.com>; Radim Krčmář <rkrcmar@...hat.com>; Thomas Gleixner
> <tglx@...utronix.de>; Ingo Molnar <mingo@...hat.com>; Borislav Petkov <bp@...en8.de>; H. Peter Anvin <hpa@...or.com>;
> x86@...nel.org
> Cc: kvm@...r.kernel.org; linux-kernel@...r.kernel.org; Gustavo A. R. Silva <gustavo@...eddedor.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@...eddedor.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@...el.com>

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