On Mon, Jul 10, 2017 at 09:55:53AM -0500, Bjorn Helgaas wrote:
> On Mon, Jul 10, 2017 at 01:34:09PM +0100, Lorenzo Pieralisi wrote:
> > If pci_scan_root_bus() fails (ie returns NULL) pcibios_scan_bus() must
> > return immediately since the struct pci_bus pointer it returns is not
> > valid and cannot be used.
> >
> > Move code checking the pci_scan_root_bus() return value to reinstate
> > proper pcibios_scanbus() error path behaviour.
> >
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> > Cc: Paul Burton <paul.burton@xxxxxxxxxx>
> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> I agree this is certainly broken. In fact, I think I broke it with
> 9e808eb6a768 ("PCI: Cleanup control flow") in 2015. So probably v4.14
> material?
Yes that makes sense, I spotted it since I am preparing patches to
remove pci_fixup_irqs() from the kernel (by removing it from all arches
that still use it), I think that technically:
88555b481958 ("MIPS: PCI: Support for CONFIG_PCI_DOMAINS_GENERIC")
created a possible breakage (ie by using the possible NULL bus pointer),
if you merge it in one branch for 4.14 I will base the pci_fixup_irqs()
removal on top of it and post the series, just let me know please.
Thanks !
Lorenzo
> > ---
> > arch/mips/pci/pci-legacy.c | 10 +++++-----
> > 1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/mips/pci/pci-legacy.c b/arch/mips/pci/pci-legacy.c
> > index 174575a..71d62f8 100644
> > --- a/arch/mips/pci/pci-legacy.c
> > +++ b/arch/mips/pci/pci-legacy.c
> > @@ -89,16 +89,16 @@ static void pcibios_scanbus(struct pci_controller *hose)
> > pci_add_resource(&resources, hose->busn_resource);
> > bus = pci_scan_root_bus(NULL, next_busno, hose->pci_ops, hose,
> > &resources);
> > - hose->bus = bus;
> > -
> > - need_domain_info = need_domain_info || pci_domain_nr(bus);
> > - set_pci_need_domain_info(hose, need_domain_info);
> > -
> > if (!bus) {
> > pci_free_resource_list(&resources);
> > return;
> > }
> >
> > + hose->bus = bus;
> > +
> > + need_domain_info = need_domain_info || pci_domain_nr(bus);
> > + set_pci_need_domain_info(hose, need_domain_info);
> > +
> > next_busno = bus->busn_res.end + 1;
> > /* Don't allow 8-bit bus number overflow inside the hose -
> > reserve some space for bridges. */
> > --
> > 2.10.0
> >
