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When checking a new device's descriptors, the USB core does not check for duplicate endpoint addresses. This can cause a problem when the sysfs files for those endpoints are created; trying to create multiple files with the same name will provoke a WARNING: WARNING: CPU: 2 PID: 865 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x8a/0xa0 sysfs: cannot create duplicate filename '/devices/platform/dummy_hcd.0/usb2/2-1/2-1:64.0/ep_05' Kernel panic - not syncing: panic_on_warn set ... CPU: 2 PID: 865 Comm: kworker/2:1 Not tainted 4.9.0-rc7+ #34 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Workqueue: usb_hub_wq hub_event ffff88006bee64c8 ffffffff81f96b8a ffffffff00000001 1ffff1000d7dcc2c ffffed000d7dcc24 0000000000000001 0000000041b58ab3 ffffffff8598b510 ffffffff81f968f8 ffffffff850fee20 ffffffff85cff020 dffffc0000000000 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff81f96b8a>] dump_stack+0x292/0x398 lib/dump_stack.c:51 [<ffffffff8168c88e>] panic+0x1cb/0x3a9 kernel/panic.c:179 [<ffffffff812b80b4>] __warn+0x1c4/0x1e0 kernel/panic.c:542 [<ffffffff812b8195>] warn_slowpath_fmt+0xc5/0x110 kernel/panic.c:565 [<ffffffff819e70ca>] sysfs_warn_dup+0x8a/0xa0 fs/sysfs/dir.c:30 [<ffffffff819e7308>] sysfs_create_dir_ns+0x178/0x1d0 fs/sysfs/dir.c:59 [< inline >] create_dir lib/kobject.c:71 [<ffffffff81fa1b07>] kobject_add_internal+0x227/0xa60 lib/kobject.c:229 [< inline >] kobject_add_varg lib/kobject.c:366 [<ffffffff81fa2479>] kobject_add+0x139/0x220 lib/kobject.c:411 [<ffffffff82737a63>] device_add+0x353/0x1660 drivers/base/core.c:1088 [<ffffffff82738d8d>] device_register+0x1d/0x20 drivers/base/core.c:1206 [<ffffffff82cb77d3>] usb_create_ep_devs+0x163/0x260 drivers/usb/core/endpoint.c:195 [<ffffffff82c9f27b>] create_intf_ep_devs+0x13b/0x200 drivers/usb/core/message.c:1030 [<ffffffff82ca39d3>] usb_set_configuration+0x1083/0x18d0 drivers/usb/core/message.c:1937 [<ffffffff82cc9e2e>] generic_probe+0x6e/0xe0 drivers/usb/core/generic.c:172 [<ffffffff82caa7fa>] usb_probe_device+0xaa/0xe0 drivers/usb/core/driver.c:263 This patch prevents the problem by checking for duplicate endpoint addresses during enumeration and skipping any duplicates. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-by: Andrey Konovalov <andreyknvl@google.com> Tested-by: Andrey Konovalov <andreyknvl@google.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 ("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.