On Mon, 26 Jun 2017 10:08:55 +0100 Russell King - ARM Linux <linux@xxxxxxxxxxxxxxx> wrote: > On Tue, Jun 20, 2017 at 09:48:31AM -0600, Alex Williamson wrote: > > If a device is bound to a non-vfio, non-whitelisted driver while a > > group is in use, then the integrity of the group is compromised and > > will result in hitting a BUG_ON. This code tries to avoid this case > > by mangling driver_override to force a no-match for the driver. The > > driver-core will either follow-up with a DRIVER_NOT_BOUND (preferred) > > or BOUND_DRIVER, at which point we can remove the driver_override > > mangling. > > Rather than mangling the driver override string to prevent driver binding, > I wonder if it would make more sense to allow the BUS_NOTIFY_BIND_DRIVER > notifier to fail the device probe? Well, it seemed like a good idea, but I don't think we're getting any traction here, the thread has gone cold: https://lkml.org/lkml/2017/6/27/1002 Greg, any further comments? > The driver override strings are, after all, exposed to userspace, and > it strikes me that this kind of mangling is racy - userspace can read > or change the override string at any time. As an alternative, I think we can make this not racy. BIND_DRIVER is notified through device_bind_driver() which specifies that the device lock is held. This covers not only BIND_DRIVER, but also BOUND_DRIVER and DRIVER_NOT_BOUND. So if the user entry points in sysfs were to require the device lock, we could easily mangle and de-mangle without interference from a user. It also seems like a rather good idea in general to exclude the user from changing driver_override while we're evaluating a match using it. Do you still have an objection to mangling driver_override if we can avoid the user race? Thanks, Alex
