linux-kernel - Re: [PATCH] arm64: kvm: avoid overflow in integer division

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Message-Id: <85a2cc47-dd95-4c39-82ab-8bf7a2a1589a@app.fastmail.com>
Date:   Thu, 18 May 2023 14:14:46 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Marc Zyngier" <maz@...nel.org>, "Arnd Bergmann" <arnd@...nel.org>
Cc:     "Oliver Upton" <oliver.upton@...ux.dev>,
        "Catalin Marinas" <catalin.marinas@....com>,
        "Will Deacon" <will@...nel.org>,
        "Shaoqin Huang" <shahuang@...hat.com>,
        "Ricardo Koller" <ricarkol@...gle.com>,
        "Gavin Shan" <gshan@...hat.com>,
        "James Morse" <james.morse@....com>,
        "Suzuki K Poulose" <suzuki.poulose@....com>,
        "Zenghui Yu" <yuzenghui@...wei.com>,
        "Cornelia Huck" <cohuck@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: kvm: avoid overflow in integer division

On Thu, May 18, 2023, at 09:30, Marc Zyngier wrote:
> On Wed, 17 May 2023 21:23:39 +0100,
> Arnd Bergmann <arnd@...nel.org> wrote:
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 3386bd28d267..6db9ef288ec3 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -92,8 +92,8 @@ static int kvm_mmu_split_nr_page_tables(u64 range)
>>  	int n = 0;
>>  
>>  	if (KVM_PGTABLE_MIN_BLOCK_LEVEL < 2)
>> -		n += DIV_ROUND_UP_ULL(range, PUD_SIZE);
>> -	n += DIV_ROUND_UP_ULL(range, PMD_SIZE);
>> +		n += DIV_ROUND_UP(range, PUD_SIZE);
>> +	n += DIV_ROUND_UP(range, PMD_SIZE);
>>  	return n;
>>  }
>
> This is against -next, right? Oliver, I assume you'll take this as a
> fix for Ricardo's series?

Yes, correct, I saw it after rebasing my tree from 6.4-rc2 to the
latest -next.

     Arnd