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@xxxxxxxxxxxxxxx>
Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
---
drivers/usb/core/hub.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 86658a81d284..00c3506324e4 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -4700,8 +4700,6 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
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);
@@ -5016,7 +5014,6 @@ hub_port_init(struct usb_hub *hub, struct usb_device *udev, int port1,
hub_port_disable(hub, port1, 0);
update_devnum(udev, devnum); /* for disconnect processing */
}
- mutex_unlock(hcd->address0_mutex);
return retval;
}
@@ -5246,6 +5243,9 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
unit_load = 100;
status = 0;
+
+ mutex_lock(hcd->address0_mutex);
+
for (i = 0; i < PORT_INIT_TRIES; i++) {
/* reallocate for each attempt, since references
@@ -5282,6 +5282,8 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
if (status < 0)
goto loop;
+ mutex_unlock(hcd->address0_mutex);
+
if (udev->quirks & USB_QUIRK_DELAY_INIT)
msleep(2000);
@@ -5370,6 +5372,7 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
loop_disable:
hub_port_disable(hub, port1, 1);
+ mutex_lock(hcd->address0_mutex);
loop:
usb_ep0_reinit(udev);
release_devnum(udev);
@@ -5396,6 +5399,8 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
}
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)
@@ -5915,6 +5920,8 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
bos = udev->bos;
udev->bos = NULL;
+ mutex_lock(hcd->address0_mutex);
+
for (i = 0; i < PORT_INIT_TRIES; ++i) {
/* ep0 maxpacket size may change; let the HCD know about it.
@@ -5924,6 +5931,7 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
if (ret >= 0 || ret == -ENOTCONN || ret == -ENODEV)
break;
}
+ mutex_unlock(hcd->address0_mutex);
if (ret < 0)
goto re_enumerate;
--
2.25.1
