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Commit feb26ac3 authored by Chris Bainbridge's avatar Chris Bainbridge Committed by Greg Kroah-Hartman
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usb: core: hub: hub_port_init lock controller instead of bus 

The XHCI controller presents two USB buses to the system - one for USB2
and one for USB3. The hub init code (hub_port_init) is reentrant but
only locks one bus per thread, leading to a race condition failure when
two threads attempt to simultaneously initialise a USB2 and USB3 device:

[    8.034843] xhci_hcd 0000:00:14.0: Timeout while waiting for setup device command
[   13.183701] usb 3-3: device descriptor read/all, error -110

On a test system this failure occurred on 6% of all boots.

The call traces at the point of failure are:

Call Trace:
 [<ffffffff81b9bab7>] schedule+0x37/0x90
 [<ffffffff817da7cd>] usb_kill_urb+0x8d/0xd0
 [<ffffffff8111e5e0>] ? wake_up_atomic_t+0x30/0x30
 [<ffffffff817dafbe>] usb_start_wait_urb+0xbe/0x150
 [<ffffffff817db10c>] usb_control_msg+0xbc/0xf0
 [<ffffffff817d07de>] hub_port_init+0x51e/0xb70
 [<ffffffff817d4697>] hub_event+0x817/0x1570
 [<ffffffff810f3e6f>] process_one_work+0x1ff/0x620
 [<ffffffff810f3dcf>] ? process_one_work+0x15f/0x620
 [<ffffffff810f4684>] worker_thread+0x64/0x4b0
 [<ffffffff810f4620>] ? rescuer_thread+0x390/0x390
 [<ffffffff810fa7f5>] kthread+0x105/0x120
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200
 [<ffffffff81ba183f>] ret_from_fork+0x3f/0x70
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200

Call Trace:
 [<ffffffff817fd36d>] xhci_setup_device+0x53d/0xa40
 [<ffffffff817fd87e>] xhci_address_device+0xe/0x10
 [<ffffffff817d047f>] hub_port_init+0x1bf/0xb70
 [<ffffffff811247ed>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffff817d4697>] hub_event+0x817/0x1570
 [<ffffffff810f3e6f>] process_one_work+0x1ff/0x620
 [<ffffffff810f3dcf>] ? process_one_work+0x15f/0x620
 [<ffffffff810f4684>] worker_thread+0x64/0x4b0
 [<ffffffff810f4620>] ? rescuer_thread+0x390/0x390
 [<ffffffff810fa7f5>] kthread+0x105/0x120
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200
 [<ffffffff81ba183f>] ret_from_fork+0x3f/0x70
 [<ffffffff810fa6f0>] ? kthread_create_on_node+0x200/0x200

Which results from the two call chains:

hub_port_init
 usb_get_device_descriptor
  usb_get_descriptor
   usb_control_msg
    usb_internal_control_msg
     usb_start_wait_urb
      usb_submit_urb / wait_for_completion_timeout / usb_kill_urb

hub_port_init
 hub_set_address
  xhci_address_device
   xhci_setup_device

Mathias Nyman explains the current behaviour violates the XHCI spec:

 hub_port_reset() will end up moving the corresponding xhci device slot
 to default state.

 As hub_port_reset() is called several times in hub_port_init() it
 sounds reasonable that we could end up with two threads having their
 xhci device slots in default state at the same time, which according to
 xhci 4.5.3 specs still is a big no no:

 "Note: Software shall not transition more than one Device Slot to the
  Default State at a time"

 So both threads fail at their next task after this.
 One fails to read the descriptor, and the other fails addressing the
 device.

Fix this in hub_port_init by locking the USB controller (instead of an
individual bus) to prevent simultaneous initialisation of both buses.

Fixes: 638139eb ("usb: hub: allow to process more usb hub events in parallel")
Link: https://lkml.org/lkml/2016/2/8/312
Link: https://lkml.org/lkml/2016/2/4/748


Signed-off-by: default avatarChris Bainbridge <chris.bainbridge@gmail.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: default avatarMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent edc8c54b

drivers/usb/core/hcd.c

+13 −2
Original line number Original line Diff line number Diff line
@@ -994,7 +994,7 @@ static void usb_bus_init (struct usb_bus *bus) 
	bus->bandwidth_allocated = 0;

	bus->bandwidth_allocated = 0;

	bus->bandwidth_int_reqs  = 0;

	bus->bandwidth_int_reqs  = 0;

	bus->bandwidth_isoc_reqs = 0;

	bus->bandwidth_isoc_reqs = 0;

	mutex_init(&bus->usb_address0_mutex);

	mutex_init(&bus->devnum_next_mutex);

}

}





/*-------------------------------------------------------------------------*/

/*-------------------------------------------------------------------------*/
@@ -2521,6 +2521,14 @@ struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver, 
		return NULL;

		return NULL;

	}

	}

	if (primary_hcd == NULL) {

	if (primary_hcd == NULL) {

		hcd->address0_mutex = kmalloc(sizeof(*hcd->address0_mutex),

				GFP_KERNEL);

		if (!hcd->address0_mutex) {

			kfree(hcd);

			dev_dbg(dev, "hcd address0 mutex alloc failed\n");

			return NULL;

		}

		mutex_init(hcd->address0_mutex);

		hcd->bandwidth_mutex = kmalloc(sizeof(*hcd->bandwidth_mutex),

		hcd->bandwidth_mutex = kmalloc(sizeof(*hcd->bandwidth_mutex),

				GFP_KERNEL);

				GFP_KERNEL);

		if (!hcd->bandwidth_mutex) {

		if (!hcd->bandwidth_mutex) {
@@ -2532,6 +2540,7 @@ struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver, 
		dev_set_drvdata(dev, hcd);

		dev_set_drvdata(dev, hcd);

	} else {

	} else {

		mutex_lock(&usb_port_peer_mutex);

		mutex_lock(&usb_port_peer_mutex);

		hcd->address0_mutex = primary_hcd->address0_mutex;

		hcd->bandwidth_mutex = primary_hcd->bandwidth_mutex;

		hcd->bandwidth_mutex = primary_hcd->bandwidth_mutex;

		hcd->primary_hcd = primary_hcd;

		hcd->primary_hcd = primary_hcd;

		primary_hcd->primary_hcd = primary_hcd;

		primary_hcd->primary_hcd = primary_hcd;
@@ -2598,8 +2607,10 @@ static void hcd_release(struct kref *kref) 
	struct usb_hcd *hcd = container_of (kref, struct usb_hcd, kref);

	struct usb_hcd *hcd = container_of (kref, struct usb_hcd, kref);





	mutex_lock(&usb_port_peer_mutex);

	mutex_lock(&usb_port_peer_mutex);

	if (usb_hcd_is_primary_hcd(hcd))

	if (usb_hcd_is_primary_hcd(hcd)) {

		kfree(hcd->address0_mutex);

		kfree(hcd->bandwidth_mutex);

		kfree(hcd->bandwidth_mutex);

	}

	if (hcd->shared_hcd) {

	if (hcd->shared_hcd) {

		struct usb_hcd *peer = hcd->shared_hcd;

		struct usb_hcd *peer = hcd->shared_hcd;

drivers/usb/core/hub.c

+4 −4
Original line number Original line Diff line number Diff line
@@ -2082,7 +2082,7 @@ static void choose_devnum(struct usb_device *udev) 
	struct usb_bus	*bus = udev->bus;

	struct usb_bus	*bus = udev->bus;





	/* be safe when more hub events are proceed in parallel */

	/* be safe when more hub events are proceed in parallel */

	mutex_lock(&bus->usb_address0_mutex);

	mutex_lock(&bus->devnum_next_mutex);

	if (udev->wusb) {

	if (udev->wusb) {

		devnum = udev->portnum + 1;

		devnum = udev->portnum + 1;

		BUG_ON(test_bit(devnum, bus->devmap.devicemap));

		BUG_ON(test_bit(devnum, bus->devmap.devicemap));
@@ -2100,7 +2100,7 @@ static void choose_devnum(struct usb_device *udev) 
		set_bit(devnum, bus->devmap.devicemap);

		set_bit(devnum, bus->devmap.devicemap);

		udev->devnum = devnum;

		udev->devnum = devnum;

	}

	}

	mutex_unlock(&bus->usb_address0_mutex);

	mutex_unlock(&bus->devnum_next_mutex);

}

}





static void release_devnum(struct usb_device *udev)

static void release_devnum(struct usb_device *udev)
@@ -4366,7 +4366,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1, 
	if (oldspeed == USB_SPEED_LOW)

	if (oldspeed == USB_SPEED_LOW)

		delay = HUB_LONG_RESET_TIME;

		delay = HUB_LONG_RESET_TIME;





	mutex_lock(&hdev->bus->usb_address0_mutex);

	mutex_lock(hcd->address0_mutex);





	/* Reset the device; full speed may morph to high speed */

	/* Reset the device; full speed may morph to high speed */

	/* FIXME a USB 2.0 device may morph into SuperSpeed on reset. */

	/* FIXME a USB 2.0 device may morph into SuperSpeed on reset. */
@@ -4652,7 +4652,7 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1, 
		hub_port_disable(hub, port1, 0);

		hub_port_disable(hub, port1, 0);

		update_devnum(udev, devnum);	/* for disconnect processing */

		update_devnum(udev, devnum);	/* for disconnect processing */

	}

	}

	mutex_unlock(&hdev->bus->usb_address0_mutex);

	mutex_unlock(hcd->address0_mutex);

	return retval;

	return retval;

}

}

include/linux/usb.h

+1 −2
Original line number Original line Diff line number Diff line
@@ -374,13 +374,12 @@ struct usb_bus { 




	int devnum_next;		/* Next open device number in

	int devnum_next;		/* Next open device number in

					 * round-robin allocation */

					 * round-robin allocation */

	struct mutex devnum_next_mutex; /* devnum_next mutex */





	struct usb_devmap devmap;	/* device address allocation map */

	struct usb_devmap devmap;	/* device address allocation map */

	struct usb_device *root_hub;	/* Root hub */

	struct usb_device *root_hub;	/* Root hub */

	struct usb_bus *hs_companion;	/* Companion EHCI bus, if any */

	struct usb_bus *hs_companion;	/* Companion EHCI bus, if any */





	struct mutex usb_address0_mutex; /* unaddressed device mutex */



	int bandwidth_allocated;	/* on this bus: how much of the time

	int bandwidth_allocated;	/* on this bus: how much of the time

					 * reserved for periodic (intr/iso)

					 * reserved for periodic (intr/iso)

					 * requests is used, on average?

					 * requests is used, on average?

include/linux/usb/hcd.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -181,6 +181,7 @@ struct usb_hcd { 
	 * bandwidth_mutex should be dropped after a successful control message

	 * bandwidth_mutex should be dropped after a successful control message

	 * to the device, or resetting the bandwidth after a failed attempt.

	 * to the device, or resetting the bandwidth after a failed attempt.

	 */

	 */

	struct mutex		*address0_mutex;

	struct mutex		*bandwidth_mutex;

	struct mutex		*bandwidth_mutex;

	struct usb_hcd		*shared_hcd;

	struct usb_hcd		*shared_hcd;

	struct usb_hcd		*primary_hcd;

	struct usb_hcd		*primary_hcd;