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commit6ae6dc22d2upstream. 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:638139eb95("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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.