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Date: Thu, 11 Feb 2016 15:11:09 +1100
From: Paul Mackerras <paulus@ozlabs.org>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: David Gibson <david@gibson.dropbear.id.au>,
 linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH kernel v2 1/6] KVM: PPC: Rework H_PUT_TCE/H_GET_TCE
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On Fri, Jan 22, 2016 at 12:59:47PM +1100, Alexey Kardashevskiy wrote:
> On 01/22/2016 11:42 AM, David Gibson wrote:
> >On Thu, Jan 21, 2016 at 06:39:32PM +1100, Alexey Kardashevskiy wrote:
[snip]
> >>+	if ((ioba & mask) || (idx + npages > size))
> >
> >It doesn't matter for the current callers, but you should check for
> >overflow in idx + npages as well.
> 
> 
> npages can be only 1..512 and this is checked in H_PUT_TCE/etc handlers.
> idx is 52bit long max.
> And this is not going to change because H_PUT_TCE_INDIRECT will always be
> limited by 512 (or one 4K page).
> 
> Do I still need the overflow check here?

You could add "|| npages > TCES_PER_PAGE" and that would make it clear
that there can't be any overflow, and it should get removed by the
compiler for the calls with constant npages.

Paul.