Subject: CVE-2022-48838: usb: gadget: Fix use-after-free bug by not setting udc->dev.driver

From: Greg Kroah-Hartman <[email-masked]>

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

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

usb: gadget: Fix use-after-free bug by not setting udc->dev.driver

The syzbot fuzzer found a use-after-free bug:

BUG: KASAN: use-after-free in dev_uevent+0x712/0x780 drivers/base/core.c:2320
Read of size 8 at addr ffff88802b934098 by task udevd/3689

CPU: 2 PID: 3689 Comm: udevd Not tainted 5.17.0-rc4-syzkaller-00229-g4f12b742eb2b #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255
 __kasan_report mm/kasan/report.c:442 [inline]
 kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
 dev_uevent+0x712/0x780 drivers/base/core.c:2320
 uevent_show+0x1b8/0x380 drivers/base/core.c:2391
 dev_attr_show+0x4b/0x90 drivers/base/core.c:2094

Although the bug manifested in the driver core, the real cause was a
race with the gadget core.  dev_uevent() does:

	if (dev->driver)
		add_uevent_var(env, "DRIVER=%s", dev->driver->name);

and between the test and the dereference of dev->driver, the gadget
core sets dev->driver to NULL.

The race wouldn't occur if the gadget core registered its devices on
a real bus, using the standard synchronization techniques of the
driver core.  However, it's not necessary to make such a large change
in order to fix this bug; all we need to do is make sure that
udc->dev.driver is always NULL.

In fact, there is no reason for udc->dev.driver ever to be set to
anything, let alone to the value it currently gets: the address of the
gadget's driver.  After all, a gadget driver only knows how to manage
a gadget, not how to manage a UDC.

This patch simply removes the statements in the gadget core that touch
udc->dev.driver.

The Linux kernel CVE team has assigned CVE-2022-48838 to this issue.

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

	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 4.9.308 with commit 4325124dde67
	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 4.14.273 with commit e2d3a7009e50
	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 4.19.236 with commit 609a7119bffe
	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 5.4.187 with commit 2282a6eb6d4e
	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 5.10.108 with commit 00bdd9bf1ac6
	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 5.15.31 with commit 2015c23610cd
	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 5.16.17 with commit 27d64436984f
	Issue introduced in 3.1 with commit 2ccea03a8f7e and fixed in 5.17 with commit 16b1941eac2b

Please see https://www.kernel.org for 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-2022-48838
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/gadget/udc/core.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/4325124dde6726267813c736fee61226f1d38f0b
	https://git.kernel.org/stable/c/e2d3a7009e505e120805f449c832942660f3f7f3
	https://git.kernel.org/stable/c/609a7119bffe3ddd7c93f2fa65be8917e02a0b7e
	https://git.kernel.org/stable/c/2282a6eb6d4e118e294e43dcc421e0e0fe4040b5
	https://git.kernel.org/stable/c/00bdd9bf1ac6d401ad926d3d8df41b9f1399f646
	https://git.kernel.org/stable/c/2015c23610cd0efadaeca4d3a8d1dae9a45aa35a
	https://git.kernel.org/stable/c/27d64436984fb8835a8b7e95993193cc478b162e
	https://git.kernel.org/stable/c/16b1941eac2bd499f065a6739a40ce0011a3d740