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From:   Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Date:   Wed, 12 Apr 2023 16:52:23 +0200
Message-ID: <CAEivzxfxm9Kg-ap9QeceGgTeCd0du7FrH7Kmi2dRZH6gah-8HQ@mail.gmail.com>
Subject: Re: [PATCH 1/2] KVM: SVM: free sev_*asid_bitmap init if SEV init fails
To:     Zhi Wang <zhi.wang.linux@gmail.com>
Cc:     pbonzini@redhat.com, Sean Christopherson <seanjc@google.com>,
        =?UTF-8?Q?St=C3=A9phane_Graber?= <stgraber@ubuntu.com>,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
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On Tue, Apr 11, 2023 at 9:47=E2=80=AFPM Zhi Wang <zhi.wang.linux@gmail.com>=
 wrote:
>
> On Tue,  4 Apr 2023 14:26:51 +0200
> Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.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@google.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> > Cc: St=C3=A9phane Graber <stgraber@ubuntu.com>
> > Cc: kvm@vger.kernel.org
> > Cc: linux-kernel@vger.kernel.org
> > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.c=
om>
> > ---
> >  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 =3D 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 =3D NULL;
> > +             bitmap_free(sev_asid_bitmap);
> > +             sev_asid_bitmap =3D NULL;
> >               goto out;
> > +     }
> >
> >       pr_info("SEV supported: %u ASIDs\n", sev_asid_count);
> >       sev_supported =3D true;
>
> It would be nice that another case can also be fixed:
>
>         sev_es_asid_count =3D 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
=3D true and everything is fine.

>
> Maybe it would be a good idea to factor out an common error handling path=
.