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SubjectRe: [BUG] Deferred probing in driver model is racy, resulting in lost probes
On Wed, Sep 26, 2012 at 09:23:21PM +0100, Russell King - ARM Linux wrote:
> 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...

Good catch. Ming, care to redo this?

greg k-h


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