Re: [PATCH] pci: assert that irqnum is between 0 and bus->nirqs in pci_change_irq_level()

[Philippe Mathieu-Daudé]

+Igor/Julia

On 10/11/20 10:27 AM, Mark Cave-Ayland wrote:
> On 11/10/2020 09:20, Mark Cave-Ayland wrote:
>
> > These assertions similar to those in the adjacent pci_bus_get_irq_level() 
> > function
> > ensure that irqnum lies within the valid PCI bus IRQ range.
> >
> > Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> > ---
> >
> > This would have immediately picked up on the sabre PCI bus IRQ overflow fixed by
> > the patch I just posted.
> >
> > ---
> >   hw/pci/pci.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index 3c8f10b461..b1484b3747 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -258,6 +258,8 @@ static void pci_change_irq_level(PCIDevice *pci_dev, int 
> > irq_num, int change)
> >               break;
> >           pci_dev = bus->parent_dev;
> >       }
> > +    assert(irq_num >= 0);
> > +    assert(irq_num < bus->nirq);
> >       bus->irq_count[irq_num] += change;
> >       bus->set_irq(bus->irq_opaque, irq_num, bus->irq_count[irq_num] != 0);
> >   }
>
> Actually something else is odd here: I've just done a quick check on the 
> callers to
> pci_change_irq_level() and it appears that both pci_update_irq_disabled() and
> pci_irq_handler() assume that irqnum is a PCI device IRQ i.e between 0 and 3, 
> whereas
> pci_change_irq_level() assumes it is working with a PCI bus IRQ between 0 and 
> bus->nirqs.

IIUC pci_map_irq_fn() returns [0..3] (PCI_NUM_PINS).

> It feels like pci_change_irq_level() should be renamed to 
> pci_bus_change_irq_level()

I don't think so, maybe extracted?

-- >8 --
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 100c9381c2f..79fb94394cc 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -248,6 +248,12 @@ static inline void pci_set_irq_state(PCIDevice *d, 
int irq_num, int level)
         d->irq_state |= level << irq_num;
 }

+static void pci_bus_change_irq_level(PCIBus *bus, int irq_num, int change)
+{
+    assert(irq_num >= 0);
+    assert(irq_num < bus->nirq);
+    bus->irq_count[irq_num] += change;
+    bus->set_irq(bus->irq_opaque, irq_num, bus->irq_count[irq_num] != 0);
+}
+
 static void pci_change_irq_level(PCIDevice *pci_dev, int irq_num, int 
change)
 {
     PCIBus *bus;
@@ -258,8 +264,7 @@ static void pci_change_irq_level(PCIDevice *pci_dev, 
int irq_num, int change)
             break;
         pci_dev = bus->parent_dev;
     }
-    bus->irq_count[irq_num] += change;
-    bus->set_irq(bus->irq_opaque, irq_num, bus->irq_count[irq_num] != 0);
+    pci_bus_change_irq_level(bus, irq_num, change);
 }
---

> similar to pci_bus_get_irq_level() but in that case are 
> pci_update_irq_disabled() and
> pci_irq_handler() both incorrect?
>
>
> ATB,
>
> Mark.