Re: [Qemu-devel] [PATCH RFC 4/7] hw/apci: fix pcihp io initialization

[Marcel Apfelbaum]

On 06/21/2016 02:19 PM, Igor Mammedov wrote:
> On Tue, 21 Jun 2016 11:57:29 +0300
> Marcel Apfelbaum <address@hidden> wrote:
>
> > On 06/17/2016 12:04 PM, Igor Mammedov wrote:
> > > On Tue, 31 May 2016 20:48:35 +0300
> > > Marcel Apfelbaum <address@hidden> wrote:
> > >
> > > > The pm initialization code assigns the pcihp IO base and length to
> > > > -1 on error, but the later code will assume 0 as invalid value.
> > > >
> > > > Fix it initializing the above value to 0 as expected.
> > > >
> > > > Signed-off-by: Marcel Apfelbaum <address@hidden>
> > > > ---
> > > >    hw/i386/acpi-build.c | 10 ++++++----
> > > >    1 file changed, 6 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > > index 0c329fb..2097c4c 100644
> > > > --- a/hw/i386/acpi-build.c
> > > > +++ b/hw/i386/acpi-build.c
> > > > @@ -124,17 +124,19 @@ static void acpi_get_pm_info(AcpiPmInfo *pm)
> > > >        Object *lpc = ich9_lpc_find();
> > > >        Object *obj = NULL;
> > > >        QObject *o;
> > > > +    int pcihp_io_len, pcihp_io_base;
> > > >
> > > >        pm->cpu_hp_io_base = 0;
> > > > -    pm->pcihp_io_base = 0;
> > > > -    pm->pcihp_io_len = 0;
> > > this introduces uninitialized memory access in q35 case
> >
> > How? We are always checking pcihp_io_len/pcihp_io_base.
> pm->pcihp_io_len is left uninitialized in q35 case
>
> and then following build_dsdt() would cause jump on uninitialized value
>      /* reserve PCIHP resources */
>      if (pm->pcihp_io_len) {
>
> > > >        if (piix) {
> > > >            obj = piix;
> > > >            pm->cpu_hp_io_base = PIIX4_CPU_HOTPLUG_IO_BASE;
> > > > -        pm->pcihp_io_base =
> > > > +        pcihp_io_base =
> > > >                object_property_get_int(obj,
> > > > ACPI_PCIHP_IO_BASE_PROP, NULL);
> > > > -        pm->pcihp_io_len =
> > > > +        pcihp_io_len =
> > > >                object_property_get_int(obj, ACPI_PCIHP_IO_LEN_PROP,
> > > > NULL); +
> > > > +        pm->pcihp_io_base = (pcihp_io_base == -1) ? 0 :
> > > > pcihp_io_base;
> > > > +        pm->pcihp_io_len = (pcihp_io_len == -1) ? 0 :
> > > > pcihp_io_len; }
> > > >        if (lpc) {
> > > >            obj = lpc;
> > >
> > > how about something like that:
> >
> > Please see the next patch. It is only  a temporary measure, the next
> > patch initialize it right to
> > ACPI_PCIHP_IO_BASE_PROP/ACPI_PCIHP_IO_LEN_PROP. If the properties are
> > not there, they will be 0, but we are checking this everywhere.
> >
> > Also I'll prefer pm->pcihp_io_len 0 length to mean "unused" because
> > it is used widely. If you still think is a real issue, I'll change
> > this, of course.
> Maybe squash it into the next patch?


I can do that. At first I thought to make the change more readable,
but because of your point I'll squash it.

Thanks,
Marcel



> > Thanks,
> > Marcel
> >
> > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > index 4f9aec6..d753e25 100644
> > > --- a/hw/i386/acpi-build.c
> > > +++ b/hw/i386/acpi-build.c
> > > @@ -125,7 +125,7 @@ static void acpi_get_pm_info(AcpiPmInfo *pm)
> > >
> > >        pm->cpu_hp_io_base = 0;
> > >        pm->pcihp_io_base = 0;
> > > -    pm->pcihp_io_len = 0;
> > > +    pm->pcihp_io_len = UINT16_MAX;
> > >        if (piix) {
> > >            obj = piix;
> > >            pm->cpu_hp_io_base = PIIX4_CPU_HOTPLUG_IO_BASE;
> > > @@ -2053,7 +2053,7 @@ build_dsdt(GArray *table_data, BIOSLinker
> > > *linker, g_ptr_array_free(mem_ranges, true);
> > >
> > >        /* reserve PCIHP resources */
> > > -    if (pm->pcihp_io_len) {
> > > +    if (pm->pcihp_io_len != UINT16_MAX) {
> > >            dev = aml_device("PHPR");
> > >            aml_append(dev, aml_name_decl("_HID",
> > > aml_string("PNP0A06"))); aml_append(dev,