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>