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Re: [libvirt] [PATCH] qemu: Check sev capability pointer before using it



On Tue, Aug 07, 2018 at 09:05:09AM +0200, Peter Krempa wrote:
> On Tue, Aug 07, 2018 at 09:42:05 +0800, Han Han wrote:
> > https://bugzilla.redhat.com/show_bug.cgi?id=1612009
> >
> > Check sev capability pointer in function qemuGetSEVInfoToParams to avoid
> > null pointer dereferences.
> >
> > Signed-off-by: Han Han <hhan redhat com>
> > ---
> >  src/qemu/qemu_driver.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > index fb0d4a8c7a..3daaef586f 100644
> > --- a/src/qemu/qemu_driver.c
> > +++ b/src/qemu/qemu_driver.c
> > @@ -21452,6 +21452,12 @@ qemuGetSEVInfoToParams(virQEMUCapsPtr qemuCaps,
> >
> >      virCheckFlags(VIR_TYPED_PARAM_STRING_OKAY, -1);
> >
> > +    if (!sev) {
> > +        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> > +                       _("SEV is not supported in this guest"));
> > +        return -1;
> > +    }
>
> I presume the crash happens after restart of libvirtd. The real bug is
> that qemuCaps don't serialize the sev data into the status XML thus the
> pointer will be cleared and NULL after libvirtd restart.
>
> The error message reported here is then wrong since the guest/host
> support SEV but the data is not available.
>
> The crash would not happen otherwise as the function is guarded by
> checking QEMU_CAPS_SEV_GUEST.

Exactly, I'm currently working on it, Peter is right, this is not the right
fix.

Erik


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