Re: [PATCH] spapr: Fail CAS if option vector table cannot be parsed

[Greg Kurz]

On Thu, 16 Jan 2020 16:34:06 +0100
Philippe Mathieu-Daudé <address@hidden> wrote:

> Hi Greg,
> 

Hi Phil,

> On 1/16/20 4:05 PM, Greg Kurz wrote:
> > Most of the option vector helpers have assertions to check their
> > arguments aren't null. The guest can provide an arbitrary address
> > for the CAS structure that would result in such null arguments.
> > Fail CAS with H_PARAMETER instead of aborting QEMU.
> > 
> > Signed-off-by: Greg Kurz <address@hidden>
> > ---
> >   hw/ppc/spapr_hcall.c |    9 +++++++++
> >   1 file changed, 9 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> > index 84e1612595bb..051869ae20ec 100644
> > --- a/hw/ppc/spapr_hcall.c
> > +++ b/hw/ppc/spapr_hcall.c
> > @@ -1701,9 +1701,18 @@ static target_ulong 
> > h_client_architecture_support(PowerPCCPU *cpu,
> >   
> >       /* For the future use: here @ov_table points to the first option 
> > vector */
> >       ov_table = addr;
> > +    if (!ov_table) {
> > +        return H_PARAMETER;
> > +    }
> 
> This doesn't look right to check ov_table, I'd check addr directly instead:
> 

I decided to check ov_table because this is what we pass to
spapr_ovec_parse_vector() and that shouldn't be NULL.

> -- >8 --
> @@ -1679,12 +1679,16 @@ static target_ulong 
> h_client_architecture_support(PowerPCCPU *cpu,
> 
>       cas_pvr = cas_check_pvr(spapr, cpu, &addr, &raw_mode_supported, 
> &local_err);
>       if (local_err) {
>           error_report_err(local_err);
>           return H_HARDWARE;
>       }
> +    if (!addr) {
> +        // error_report*()
> +        return H_PARAMETER;
> +    }
> 

I don't really care one way or another, but adding an error_report() is a
good idea since linux just print out the following in case of CAS failure:

WARNING: ibm,client-architecture-support call FAILED!

>       /* Update CPUs */
>       if (cpu->compat_pvr != cas_pvr) {
> ---
> 
> Still I'm not sure it makes sense, because the guest can also set other 
> invalid addresses such addr=0x69.
> 

The point of this patch is just to avoid hitting the assertions. 0x69
is probably bullshit but it passes the g_assert() at least.

> >   
> >       ov1_guest = spapr_ovec_parse_vector(ov_table, 1);
> > +    if (!ov1_guest) {
> > +        return H_PARAMETER;
> > +    }
> 
> This one is OK (unlikely case where vector 1 isn't present).
> 
> >       ov5_guest = spapr_ovec_parse_vector(ov_table, 5);
> > +    if (!ov5_guest) {
> > +        return H_PARAMETER;
> > +    }
> 
> This one is OK too (unlikely case where vector 5 isn't present).
> 
> >       if (spapr_ovec_test(ov5_guest, OV5_MMU_BOTH)) {
> >           error_report("guest requested hash and radix MMU, which is 
> > invalid.");
> >           exit(EXIT_FAILURE);
> > 
> > 
>