linux-kernel - Re: [PATCH 1/2] KVM: SVM: free sev_*asid

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Message-ID: <20230413080702.0000016b.zhi.wang.linux@gmail.com>
Date:   Thu, 13 Apr 2023 08:07:02 +0300
From:   Zhi Wang <zhi.wang.linux@...il.com>
To:     Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
Cc:     pbonzini@...hat.com, Sean Christopherson <seanjc@...gle.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: SVM: free sev_*asid_bitmap init if SEV init
 fails

On Wed, 12 Apr 2023 16:52:23 +0200
Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com> wrote:

> On Tue, Apr 11, 2023 at 9:47 PM Zhi Wang <zhi.wang.linux@...il.com> wrote:
> >
> > On Tue,  4 Apr 2023 14:26:51 +0200
> > Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com> wrote:
> >
> > > If misc_cg_set_capacity() fails for some reason then we have
> > > a memleak for sev_reclaim_asid_bitmap/sev_asid_bitmap. It's
> > > not a case right now, because misc_cg_set_capacity() just can't
> > > fail and check inside it is always successful.
> > >
> > > But let's fix that for code consistency.
> > >
> > > Cc: Sean Christopherson <seanjc@...gle.com>
> > > Cc: Paolo Bonzini <pbonzini@...hat.com>
> > > Cc: Stéphane Graber <stgraber@...ntu.com>
> > > Cc: kvm@...r.kernel.org
> > > Cc: linux-kernel@...r.kernel.org
> > > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
> > > ---
> > >  arch/x86/kvm/svm/sev.c | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> > > index c25aeb550cd9..a42536a0681a 100644
> > > --- a/arch/x86/kvm/svm/sev.c
> > > +++ b/arch/x86/kvm/svm/sev.c
> > > @@ -2213,8 +2213,13 @@ void __init sev_hardware_setup(void)
> > >       }
> > >
> > >       sev_asid_count = max_sev_asid - min_sev_asid + 1;
> > > -     if (misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count))
> > > +     if (misc_cg_set_capacity(MISC_CG_RES_SEV, sev_asid_count)) {
> > > +             bitmap_free(sev_reclaim_asid_bitmap);
> > > +             sev_reclaim_asid_bitmap = NULL;
> > > +             bitmap_free(sev_asid_bitmap);
> > > +             sev_asid_bitmap = NULL;
> > >               goto out;
> > > +     }
> > >
> > >       pr_info("SEV supported: %u ASIDs\n", sev_asid_count);
> > >       sev_supported = true;
> >
> > It would be nice that another case can also be fixed:
> >
> >         sev_es_asid_count = min_sev_asid - 1;
> >         if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
> >                 goto out; /* <----HERE */
> 
> Nope.
> 
> There is no leak. Because when we are at this point then sev_supported
> = true and everything is fine.
> 
Uh. You are right. Sorry that I was giving this comment based on my on-going
development branch.
> >
> > Maybe it would be a good idea to factor out an common error handling path.