On Wed, 10 Sep 2014, Joe Lawrence wrote: > Hi Alan, > > Here is a revised patch for yesterday's use-after-free bug report. I > moved the hdev assignment and reference inside the hub_event_lock, then > returned the ref on the way out of hub_events. > > Ordering is now symmetric: > > kref_get(&hub->kref) > usb_get_dev(hdev) > usb_lock_device(hdev) > ... > usb_unlock_device(hdev) > usb_put_dev(hdev) > kref_put(&hub->kref, hub_release) > > No reports from slub_debug during lastnight's tests. > > -->8-- -->8-- > > From 5f169da5fbdb6374dc23e8202a7a06fd27196a07 Mon Sep 17 00:00:00 2001 > From: Joe Lawrence <joe.lawrence@xxxxxxxxxxx> > Date: Tue, 9 Sep 2014 17:24:41 -0400 > Subject: [PATCH] usb: hub: take hub->hdev reference when processing from > eventlist > > During surprise device hotplug removal tests, it was observed that > hub_events may try to call usb_lock_device on a device that has already > been freed. Protect the usb_device by taking out a reference (under the > hub_event_lock) when hub_events pulls it off the list, returning the > reference after hub_events is finished using it. > > Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxxx> > Suggested-by: David Bulkow <david.bulkow@xxxxxxxxxxx> for using kref > Suggested-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> for placement > --- > drivers/usb/core/hub.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > index 46f5161..d481c99 100644 > --- a/drivers/usb/core/hub.c > +++ b/drivers/usb/core/hub.c > @@ -5024,9 +5024,10 @@ static void hub_events(void) > > hub = list_entry(tmp, struct usb_hub, event_list); > kref_get(&hub->kref); > + hdev = hub->hdev; > + usb_get_dev(hdev); > spin_unlock_irq(&hub_event_lock); > > - hdev = hub->hdev; > hub_dev = hub->intfdev; > intf = to_usb_interface(hub_dev); > dev_dbg(hub_dev, "state %d ports %d chg %04x evt %04x\n", > @@ -5139,6 +5140,7 @@ static void hub_events(void) > usb_autopm_put_interface(intf); > loop_disconnected: > usb_unlock_device(hdev); > + usb_put_dev(hdev); > kref_put(&hub->kref, hub_release); > > } /* end while (1) */ This looks fine. You can submit it to Greg and mark it for -stable. Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
