Re: [PATCH v2] KVM: Don't fail KVM_GET_SUPPORTED_CPUID if nent is just right

[Sasha Levin <levinsasha928@gmail.com>]

On Thu, 2011-11-24 at 12:48 +0200, Avi Kivity wrote:
> On 11/24/2011 12:45 PM, Sasha Levin wrote:
> > If we pass just enough entries to KVM_GET_SUPPORTED_CPUID, we would still
> > fail with -E2BIG due to wrong comparisons.
> >
> > Cc: Avi Kivity <avi@redhat.com>
> > Cc: Marcelo Tosatti <mtosatti@redhat.com>
> > Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> > ---
> >  arch/x86/kvm/x86.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 9eff4af..83fef71 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -2710,7 +2710,7 @@ static int kvm_dev_ioctl_get_supported_cpuid(struct kvm_cpuid2 *cpuid,
> >  		     cpuid->nent);
> >  
> >  	r = -E2BIG;
> > -	if (nent >= cpuid->nent)
> > +	if (nent > cpuid->nent)
> >  		goto out_free;
> >  
> >
> 
> This is just a landmine for the next entry to be added there; surely
> whoever adds it will forget to correct the > back to >=.
> 

Slapping a big warning before that should do the trick? Or maybe add
something similar to 'final_nent = nent - 1;'?

-- 

Sasha.