On Mon, Jan 12, 2015 at 11:29:15AM -0500, Alan Stern wrote:
> This seems like a good idea and the obvious (once it has been pointed
> out!) approach.
>
> Perhaps not directly related to the issue at hand is this question: In
> scsi_rescan_device() we will now have:
>
> mutex_lock(&shost->scan_mutex);
> if (dev->driver && try_module_get(dev->driver->owner)) {
> struct scsi_driver *drv = to_scsi_driver(dev->driver);
>
> if (drv->rescan)
> drv->rescan(dev);
> module_put(dev->driver->owner);
> }
> mutex_unlock(&shost->scan_mutex);
>
> What prevents the device from being unbound from its driver while the
> rescan runs? Evaluating the argument to the module_put() would then
> dereference a NULL pointer.
>
> Unbind events that happen through the normal scsi_remove_host()
> mechanism are fine, because scsi_remove_host() locks the scan_mutex.
> But what about writes to the driver's sysfs "unbind" attribute?
Looks like we should still get an unconditional reference to
the device using get_device in scsi_rescan_device at least.
But this seems like a more generic problem, and at least a quick glance at
the pci_driver methods seems like others don't have a good
synchroniation of ->remove against random driver methods.
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