CVE-2021-46930: usb: mtu3: fix list_head check warning

CVE-2021-46930: usb: mtu3: fix list_head check warning

[Greg Kroah-Hartman]

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

usb: mtu3: fix list_head check warning

This is caused by uninitialization of list_head.

BUG: KASAN: use-after-free in __list_del_entry_valid+0x34/0xe4

Call trace:
dump_backtrace+0x0/0x298
show_stack+0x24/0x34
dump_stack+0x130/0x1a8
print_address_description+0x88/0x56c
__kasan_report+0x1b8/0x2a0
kasan_report+0x14/0x20
__asan_load8+0x9c/0xa0
__list_del_entry_valid+0x34/0xe4
mtu3_req_complete+0x4c/0x300 [mtu3]
mtu3_gadget_stop+0x168/0x448 [mtu3]
usb_gadget_unregister_driver+0x204/0x3a0
unregister_gadget_item+0x44/0xa4

The Linux kernel CVE team has assigned CVE-2021-46930 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.2 with commit 83374e035b62 and fixed in 5.4.170 with commit 585e2b244dda
	Issue introduced in 5.2 with commit 83374e035b62 and fixed in 5.10.90 with commit 3b6efe0b7ba0
	Issue introduced in 5.2 with commit 83374e035b62 and fixed in 5.15.13 with commit 249ddfbe0057
	Issue introduced in 5.2 with commit 83374e035b62 and fixed in 5.16 with commit 8c313e3bfd9a

Please see https://www.kernel.org or a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-46930
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/usb/mtu3/mtu3_gadget.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/585e2b244dda7ea733274e4b8fa27853d625d3bf
	https://git.kernel.org/stable/c/3b6efe0b7ba03cc2acf0694b46d6ff33c5b4c295
	https://git.kernel.org/stable/c/249ddfbe00570d6dc76208e88017937d4d374c79
	https://git.kernel.org/stable/c/8c313e3bfd9adae8d5c4ba1cc696dcbc86fbf9bf