tree aaa70c406d82a1201f83e1a87e30ff8e9ce455d2
parent 339e9af5fc264003dec2ece442aa384e9990338b
author Mathias Nyman <mathias.nyman@linux.intel.com> 1637014590 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1638949502 +0100

usb: hub: Fix usb enumeration issue due to address0 race

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>