543d7784b0
There is a race in the hub driver between hub_disconnect() and recursively_mark_NOTATTACHED(). This race can be triggered if the driver is unbound from a device at the same time as the bus's root hub is removed. When the race occurs, it can cause an oops: BUG: unable to handle kernel NULL pointer dereference at 0000015c IP: [<c16d5fb0>] recursively_mark_NOTATTACHED+0x20/0x60 Call Trace: [<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60 [<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60 [<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60 [<c16d5fc4>] recursively_mark_NOTATTACHED+0x34/0x60 [<c16d6082>] usb_set_device_state+0x92/0x120 [<c16d862b>] usb_disconnect+0x2b/0x1a0 [<c16dd4c0>] usb_remove_hcd+0xb0/0x160 [<c19ca846>] ? _raw_spin_unlock_irqrestore+0x26/0x50 [<c1704efc>] ehci_mid_remove+0x1c/0x30 [<c1704f26>] ehci_mid_stop_host+0x16/0x30 [<c16f7698>] penwell_otg_work+0xd28/0x3520 [<c19c945b>] ? __schedule+0x39b/0x7f0 [<c19cdb9d>] ? sub_preempt_count+0x3d/0x50 [<c125e97d>] process_one_work+0x11d/0x3d0 [<c19c7f4d>] ? mutex_unlock+0xd/0x10 [<c125e0e5>] ? manage_workers.isra.24+0x1b5/0x270 [<c125f009>] worker_thread+0xf9/0x320 [<c19ca846>] ? _raw_spin_unlock_irqrestore+0x26/0x50 [<c125ef10>] ? rescuer_thread+0x2b0/0x2b0 [<c1264ac4>] kthread+0x94/0xa0 [<c19d0f77>] ret_from_kernel_thread+0x1b/0x28 [<c1264a30>] ? kthread_create_on_node+0xc0/0xc0 One problem is that recursively_mark_NOTATTACHED() uses the intfdata value and hub->hdev->maxchild while hub_disconnect() is clearing them. Another problem is that it uses hub->ports[i] while the port device is being released. To fix this race, we need to hold the device_state_lock while hub_disconnect() changes the values. (Note that usb_disconnect() and hub_port_connect_change() already acquire this lock at similar critical times during a USB device's life cycle.) We also need to remove the port devices after maxchild has been set to 0, instead of before. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-by: "Du, Changbin" <changbinx.du@intel.com> Tested-by: "Du, Changbin" <changbinx.du@intel.com> CC: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.