7b2db29fbb
If usb_get_bos_descriptor() returns an error, usb->bos will be NULL. Nevertheless, it is dereferenced unconditionally in hub_set_initial_usb2_lpm_policy() if usb2_hw_lpm_capable is set. This results in a crash. usb 5-1: unable to get BOS descriptor ... Unable to handle kernel NULL pointer dereference at virtual address 00000008 pgd = ffffffc00165f000 [00000008] *pgd=000000000174f003, *pud=000000000174f003, *pmd=0000000001750003, *pte=00e8000001751713 Internal error: Oops: 96000005 [#1] PREEMPT SMP Modules linked in: uinput uvcvideo videobuf2_vmalloc cmac [ ... ] CPU: 5 PID: 3353 Comm: kworker/5:3 Tainted: G B 4.4.52 #480 Hardware name: Google Kevin (DT) Workqueue: events driver_set_config_work task: ffffffc0c3690000 ti: ffffffc0ae9a8000 task.ti: ffffffc0ae9a8000 PC is at hub_port_init+0xc3c/0xd10 LR is at hub_port_init+0xc3c/0xd10 ... Call trace: [<ffffffc0007fbbfc>] hub_port_init+0xc3c/0xd10 [<ffffffc0007fbe2c>] usb_reset_and_verify_device+0x15c/0x82c [<ffffffc0007fc5e0>] usb_reset_device+0xe4/0x298 [<ffffffbffc0e3fcc>] rtl8152_probe+0x84/0x9b0 [r8152] [<ffffffc00080ca8c>] usb_probe_interface+0x244/0x2f8 [<ffffffc000774a24>] driver_probe_device+0x180/0x3b4 [<ffffffc000774e48>] __device_attach_driver+0xb4/0xe0 [<ffffffc000772168>] bus_for_each_drv+0xb4/0xe4 [<ffffffc0007747ec>] __device_attach+0xd0/0x158 [<ffffffc000775080>] device_initial_probe+0x24/0x30 [<ffffffc0007739d4>] bus_probe_device+0x50/0xe4 [<ffffffc000770bd0>] device_add+0x414/0x738 [<ffffffc000809fe8>] usb_set_configuration+0x89c/0x914 [<ffffffc00080a120>] driver_set_config_work+0xc0/0xf0 [<ffffffc000249bb8>] process_one_work+0x390/0x6b8 [<ffffffc00024abcc>] worker_thread+0x480/0x610 [<ffffffc000251a80>] kthread+0x164/0x178 [<ffffffc0002045d0>] ret_from_fork+0x10/0x40 Since we don't know anything about LPM capabilities without BOS descriptor, don't attempt to enable LPM if it is not available. Fixes: 890dae886721 ("xhci: Enable LPM support only for hardwired ...") Cc: stable <stable@vger.kernel.org> Cc: Mathias Nyman <mathias.nyman@linux.intel.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com> 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 ("hub_wq").
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.