On Tue, 20 Aug 2013, Krzysztof Mazur wrote: > On Tue, Aug 20, 2013 at 02:18:57PM -0400, Alan Stern wrote: > > On Tue, 20 Aug 2013, Krzysztof Mazur wrote: > > > > > Ignoring usb_hub_create_port_device() errors cause later NULL pointer > > > deference when uninitialized hub->ports[i] entries are dereferenced > > > after port memory allocation error. > > > > > > Signed-off-by: Krzysztof Mazur <krzys...@podlesie.net> > > > --- > > > I'm not sure if failing in that case is a good idea, but other solutions > > > are more complex. > > > > > > I tried also changing hdev->maxchild and skiping initialization > > > of later ports, but it didn't work because in some cases > > > hub->descriptor->bNbrPorts is used instead of hdev->maxchild. > > > With simulated usb_hub_create_port_device() failure I have an Oops > > > in hub_power_on(). > > > > I think this patch is correct. However, we also should change the > > other places that refer to bNbrPorts; make them use maxchild instead. > > Ok, I can try to catch all such cases and fix problems with > maxchild < bNBrPorts, but I think that changing bNBrPorts to maxchild > might be not enough. For instance:
We should never have maxchild < bNbrPorts (unless maxchild is 0). But just in case we do, changing the code is a good idea. Besides, "hub->maxchild" is shorter and easier to read than "hub->descriptor->bNbrPorts". :-) > for (port1 = 1; port1 <= hub->descriptor->bNbrPorts; port1++) > if (hub->ports[port1 - 1]->power_is_on) > set_port_feature(hub->hdev, port1, USB_PORT_FEAT_POWER); > else > usb_clear_port_feature(hub->hdev, port1, > USB_PORT_FEAT_POWER); > > in hub_power_on() should be probably changed to something like: > > for (port1 = 1; port1 <= hub->descriptor->bNbrPorts; port1++) > if (hub->ports[port1 - 1] && hub->ports[port1 - 1]->power_is_on) > set_port_feature(hub->hdev, port1, USB_PORT_FEAT_POWER); > else > usb_clear_port_feature(hub->hdev, port1, > USB_PORT_FEAT_POWER); > > to disable uninitialized ports. No. The ports above maxchild aren't merely uninitialized; they are completely unused. We should ignore them altogether. Just replace descriptor->bNbrPorts with maxchild. > > > Another possible solution is allowing for uninitialized ports and > > > checking for hub->ports[i] == NULL. > > > > No, if we can't allocate memory for all the ports then the whole thing > > should fail. > > The usb_hub_create_port_device() might fail also in case of device_add() > error. The main reason for errors in device_add() is memory allocation failure. Regardless, if the port structures can't be initialized then let's fail. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
