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SubjectRe: [BUG] Deferred probing in driver model is racy, resulting in lost probes
On Wed, Sep 26, 2012 at 01:08:33PM -0700, Greg Kroah-Hartman wrote:
> On Sun, Sep 16, 2012 at 09:24:43PM +0800, Ming Lei wrote:
> > diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> > index 181ed26..17d7437 100644
> > --- a/drivers/base/bus.c
> > +++ b/drivers/base/bus.c
> > @@ -714,12 +714,12 @@ int bus_add_driver(struct device_driver *drv)
> > if (error)
> > goto out_unregister;
> >
> > + klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
> > if (drv->bus->p->drivers_autoprobe) {
> > error = driver_attach(drv);
> > if (error)
> > goto out_unregister;
> > }
> > - klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
> > module_add_driver(drv->owner, drv);
> >
> > error = driver_create_file(drv, &driver_attr_uevent);
> >
> >
> >
>
> Did the above patch ever prove to solve the issue or not?

To be honest, I've not bothered to test the above patch, and now when I
look at it, I notice it's broken - in that on error it will corrupt the
driver list. Take a look at the error path.

priv is drv->p. We add priv->knode_bus to the driver list. If
driver_attach() returns an error, then we go to out_unregister, which
does:

out_unregister:
kobject_put(&priv->kobj);
kfree(drv->p);
drv->p = NULL;

thereby freeing the node we just added to the driver list without first
removing it.

I suspect it will fix the problem, but let's get the patch to be correct
before it gets tested...


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