[PATCH 3.10 020/104] USB: fix race between hub_disconnect and recursively_mark_NOTATTACHED

Greg Kroah-Hartman
2014-02-04T23:01:38Z

From: Alan Stern <stern@rowland.harvard.edu>

commit 543d7784b07ffd16cc82a9cb4e1e0323fd0040f1 upstream.

There is a race in the hub driver between hub_disconnect() and
recursively_mark_NOTATTACHED(). This race can be triggered if the
driver is unbound from a device at the same time as the bus's root hub
is removed. When the race occurs, it can cause an oops:

BUG: unable to handle kernel NULL pointer dereference at 0000015c
IP: [<c16d5fb0>] recursively_mark_NOTATTACHED+0x20/0x60
Call Trace:
[<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60
[<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60
[<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60
[<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60
[<c16d6082>] usb_set_device_state+0x92/0x120
[<c16d862b>] usb_disconnect+0x2b/0x1a0
[<c16dd4c0>] usb_remove_hcd+0xb0/0x160
[<c19ca846>] ? _raw_spin_unlock_irqrestore+0x26/0x50
[<c1704efc>] ehci_mid_remove+0x1c/0x30
[<c1704f26>] ehci_mid_stop_host+0x16/0x30
[<c16f7698>] penwell_otg_work+0xd28/0x3520
[<c19c945b>] ? __schedule+0x39b/0x7f0
[<c19cdb9d>] ? sub_preempt_count+0x3d/0x50
[<c125e97d>] process_one_work+0x11d/0x3d0
[<c19c7f4d>] ? mutex_unlock+0xd/0x10
[<c125e0e5>] ? manage_workers.isra.24+0x1b5/0x270
[<c125f009>] worker_thread+0xf9/0x320
[<c19ca846>] ? _raw_spin_unlock_irqrestore+0x26/0x50
[<c125ef10>] ? rescuer_thread+0x2b0/0x2b0
[<c1264ac4>] kthread+0x94/0xa0
[<c19d0f77>] ret_from_kernel_thread+0x1b/0x28
[<c1264a30>] ? kthread_create_on_node+0xc0/0xc0

One problem is that recursively_mark_NOTATTACHED() uses the intfdata
value and hub->hdev->maxchild while hub_disconnect() is clearing them.
Another problem is that it uses hub->ports[i] while the port device is
being released.

To fix this race, we need to hold the device_state_lock while
hub_disconnect() changes the values. (Note that usb_disconnect()
and hub_port_connect_change() already acquire this lock at similar
critical times during a USB device's life cycle.) We also need to
remove the port devices after maxchild has been set to 0, instead of
before.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: "Du, Changbin" <changbinx.du@intel.com>
Tested-by: "Du, Changbin" <changbinx.du@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/core/hub.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1605,7 +1605,7 @@ static void hub_disconnect(struct usb_in
{
struct usb_hub *hub = usb_get_intfdata(intf);
struct usb_device *hdev = interface_to_usbdev(intf);
- int i;
+ int port1;

/* Take the hub off the event list and don't let it be added again */
spin_lock_irq(&hub_event_lock);
@@ -1620,11 +1620,15 @@ static void hub_disconnect(struct usb_in
hub->error = 0;
hub_quiesce(hub, HUB_DISCONNECT);

- usb_set_intfdata (intf, NULL);
+ /* Avoid races with recursively_mark_NOTATTACHED() */
+ spin_lock_irq(&device_state_lock);
+ port1 = hdev->maxchild;
+ hdev->maxchild = 0;
+ usb_set_intfdata(intf, NULL);
+ spin_unlock_irq(&device_state_lock);

- for (i = 0; i < hdev->maxchild; i++)
- usb_hub_remove_port_device(hub, i + 1);
- hub->hdev->maxchild = 0;
+ for (; port1 > 0; --port1)
+ usb_hub_remove_port_device(hub, port1);

if (hub->hdev->speed == USB_SPEED_HIGH)
highspeed_hubs--;