linux-kernel - Re: [PATCH MANUALSEL 5.14 5/5] KVM: MMU: Reset mmu->pkru

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Date:   Tue, 26 Oct 2021 18:17:09 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     Chenyi Qiang <chenyi.qiang@...el.com>,
        Sean Christopherson <seanjc@...gle.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, huaitong.han@...el.com,
        guangrong.xiao@...ux.intel.com, kvm@...r.kernel.org
Subject: Re: [PATCH MANUALSEL 5.14 5/5] KVM: MMU: Reset mmu->pkru_mask to
 avoid stale data

On 25/10/21 22:38, Sasha Levin wrote:
> From: Chenyi Qiang <chenyi.qiang@...el.com>
> 
> [ Upstream commit a3ca5281bb771d8103ea16f0a6a8a5df9a7fb4f3 ]
> 
> When updating mmu->pkru_mask, the value can only be added but it isn't
> reset in advance. This will make mmu->pkru_mask keep the stale data.
> Fix this issue.
> 
> Fixes: 2d344105f57c ("KVM, pkeys: introduce pkru_mask to cache conditions")
> Signed-off-by: Chenyi Qiang <chenyi.qiang@...el.com>
> Message-Id: <20211021071022.1140-1-chenyi.qiang@...el.com>
> Reviewed-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>   arch/x86/kvm/mmu/mmu.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index c268fb59f779..6719a8041f59 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4465,10 +4465,10 @@ static void update_pkru_bitmask(struct kvm_mmu *mmu)
>   	unsigned bit;
>   	bool wp;
>   
> -	if (!is_cr4_pke(mmu)) {
> -		mmu->pkru_mask = 0;
> +	mmu->pkru_mask = 0;
> +
> +	if (!is_cr4_pke(mmu))
>   		return;
> -	}
>   
>   	wp = is_cr0_wp(mmu);
>   
> 

Acked-by: Paolo Bonzini <pbonzini@...hat.com>