[PATCH 4.4 04/52] usb: hub: Fix usb enumeration issue due to address0 race

Greg Kroah-Hartman
2021-12-06T14:59:02Z

From: Mathias Nyman <mathias.nyman@linux.intel.com>

commit 6ae6dc22d2d1ce6aa77a6da8a761e61aca216f8b upstream.

xHC hardware can only have one slot in default state with address 0
waiting for a unique address at a time, otherwise "undefined behavior
may occur" according to xhci spec 5.4.3.4

The address0_mutex exists to prevent this across both xhci roothubs.

If hub_port_init() fails, it may unlock the mutex and exit with a xhci
slot in default state. If the other xhci roothub calls hub_port_init()
at this point we end up with two slots in default state.

Make sure the address0_mutex protects the slot default state across
hub_port_init() retries, until slot is addressed or disabled.

Note, one known minor case is not fixed by this patch.
If device needs to be reset during resume, but fails all hub_port_init()
retries in usb_reset_and_verify_device(), then it's possible the slot is
still left in default state when address0_mutex is unlocked.

Cc: <stable@vger.kernel.org>
Fixes: 638139eb95d2 ("usb: hub: allow to process more usb hub events in parallel")
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20211115221630.871204-1-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/core/hub.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4393,8 +4393,6 @@ hub_port_init(struct usb_hub *hub, struc
if (oldspeed == USB_SPEED_LOW)
delay = HUB_LONG_RESET_TIME;

- mutex_lock(hcd->address0_mutex);
-
/* Reset the device; full speed may morph to high speed */
/* FIXME a USB 2.0 device may morph into SuperSpeed on reset. */
retval = hub_port_reset(hub, port1, udev, delay, false);
@@ -4681,7 +4679,6 @@ fail:
hub_port_disable(hub, port1, 0);
update_devnum(udev, devnum); /* for disconnect processing */
}
- mutex_unlock(hcd->address0_mutex);
return retval;
}

@@ -4826,6 +4823,9 @@ static void hub_port_connect(struct usb_
unit_load = 100;

status = 0;
+
+ mutex_lock(hcd->address0_mutex);
+
for (i = 0; i < SET_CONFIG_TRIES; i++) {

/* reallocate for each attempt, since references
@@ -4862,6 +4862,8 @@ static void hub_port_connect(struct usb_
if (status < 0)
goto loop;

+ mutex_unlock(hcd->address0_mutex);
+
if (udev->quirks & USB_QUIRK_DELAY_INIT)
msleep(2000);

@@ -4950,6 +4952,7 @@ static void hub_port_connect(struct usb_

loop_disable:
hub_port_disable(hub, port1, 1);
+ mutex_lock(hcd->address0_mutex);
loop:
usb_ep0_reinit(udev);
release_devnum(udev);
@@ -4976,6 +4979,8 @@ loop:
}

done:
+ mutex_unlock(hcd->address0_mutex);
+
hub_port_disable(hub, port1, 1);
if (hcd->driver->relinquish_port && !hub->hdev->parent) {
if (status != -ENOTCONN && status != -ENODEV)
@@ -5506,6 +5511,8 @@ static int usb_reset_and_verify_device(s
bos = udev->bos;
udev->bos = NULL;

+ mutex_lock(hcd->address0_mutex);
+
for (i = 0; i < SET_CONFIG_TRIES; ++i) {

/* ep0 maxpacket size may change; let the HCD know about it.
@@ -5515,6 +5522,7 @@ static int usb_reset_and_verify_device(s
if (ret >= 0 || ret == -ENOTCONN || ret == -ENODEV)
break;
}
+ mutex_unlock(hcd->address0_mutex);

if (ret < 0)
goto re_enumerate;