Subject: CVE-2021-46941: usb: dwc3: core: Do core softreset when switch mode

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

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

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

usb: dwc3: core: Do core softreset when switch mode

According to the programming guide, to switch mode for DRD controller,
the driver needs to do the following.

To switch from device to host:
1. Reset controller with GCTL.CoreSoftReset
2. Set GCTL.PrtCapDir(host mode)
3. Reset the host with USBCMD.HCRESET
4. Then follow up with the initializing host registers sequence

To switch from host to device:
1. Reset controller with GCTL.CoreSoftReset
2. Set GCTL.PrtCapDir(device mode)
3. Reset the device with DCTL.CSftRst
4. Then follow up with the initializing registers sequence

Currently we're missing step 1) to do GCTL.CoreSoftReset and step 3) of
switching from host to device. John Stult reported a lockup issue seen
with HiKey960 platform without these steps[1]. Similar issue is observed
with Ferry's testing platform[2].

So, apply the required steps along with some fixes to Yu Chen's and John
Stultz's version. The main fixes to their versions are the missing wait
for clocks synchronization before clearing GCTL.CoreSoftReset and only
apply DCTL.CSftRst when switching from host to device.

[1] https://lore.kernel.org/linux-usb/[email-masked]/
[2] https://lore.kernel.org/linux-usb/[email-masked]/

The Linux kernel CVE team has assigned CVE-2021-46941 to this issue.

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

	Issue introduced in 4.12 with commit 41ce1456e1db and fixed in 5.10.36 with commit fce7bbcd07d5
	Issue introduced in 4.12 with commit 41ce1456e1db and fixed in 5.11.20 with commit 800f58217626
	Issue introduced in 4.12 with commit 41ce1456e1db and fixed in 5.12.3 with commit 1c10fd60c859
	Issue introduced in 4.12 with commit 41ce1456e1db and fixed in 5.13 with commit f88359e1588b

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-2021-46941
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/dwc3/core.c
	drivers/usb/dwc3/core.h

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/fce7bbcd07d59ac30dba8ce225316b3b4c1c7b50
	https://git.kernel.org/stable/c/800f58217626c8b147aa40660e572ed8a0d56e3b
	https://git.kernel.org/stable/c/1c10fd60c8595ea7ff7e29d3cf1fa88069941da3
	https://git.kernel.org/stable/c/f88359e1588b85cf0e8209ab7d6620085f3441d9