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

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Message-ID: <20181227033545.GA15607@richard>
Date:   Thu, 27 Dec 2018 11:35:45 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Luwei Kang <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,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] KVM: x86: Fix bit shifting in update_intel_pt_cfg

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@...eddedor.com>

Looks good.

Reviewed-by: Wei Yang <richardw.yang@...ux.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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