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) */ -- 1.7.10.4 -- 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
