hotplug remove vs. device driver close

[Don Fry]

> > > We make no such guarantee.  As I stated, the Cardbus/PCMCIA handle this
> > > quite easily, so it is pretty simple to fix up a PCI driver to also
> > > handle this.
> > >
> > > But the main answer is that the PCI Hotplug spec states that the OS does
> > > NOT have to protect for this happening to regular PCI devices.
> >
> > So if I understand what you are saying: if the OS crashes because of
> > a sysadmin error or a script error during pci hotplug remove, that's
> > considered OK?
>
> As sysadmin I can delete your whole root fs, and reboot the box into
> obvilion.  Are you considering changing this ability too?  :)
>
> If you are really worried about this, then look into a different
> permisssion model for Linux like SELinux.
>
> Or you can simply fix up your PCI driver to properly handle reading all
> FF when the device has been removed.  That seems to be what you need to
> do to solve this for your small subset of drivers on your platform,
> correct?
>

The pcnet32 driver tries to do the 'right thing' when it reads 0xffff,
but that does not include doing a 'close' prior to being removed.  The
driver could keep some state around so that if its remove routine was
called without close first, it would cleanup, but I don't know of any
network driver that does this.

The remove with a close is where the leak/crash might occur.

> > I understand why the PCI spec would say that: they have no desire
> > to over-burden already struggling OS developers: the PCI spec
> > committee probably thinks in terms of "provide function not policy".
> > That's normal and as it should be.
>
> That's also what the kernel provides, function not policy.  Put your
> policy in userspace and force your admin to use a tool that ensures that
> the device has properly shutdown anything that is bound to that device
> before it tells the kernel to remove it from the system.
>
> thanks,
>
> greg k-h
--
Don Fry
brazilnut at us.ibm.com

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