Subject: CVE-2023-52488: serial: sc16is7xx: convert from _raw_ to _noinc_ regmap functions for FIFO

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

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

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

serial: sc16is7xx: convert from _raw_ to _noinc_ regmap functions for FIFO

The SC16IS7XX IC supports a burst mode to access the FIFOs where the
initial register address is sent ($00), followed by all the FIFO data
without having to resend the register address each time. In this mode, the
IC doesn't increment the register address for each R/W byte.

The regmap_raw_read() and regmap_raw_write() are functions which can
perform IO over multiple registers. They are currently used to read/write
from/to the FIFO, and although they operate correctly in this burst mode on
the SPI bus, they would corrupt the regmap cache if it was not disabled
manually. The reason is that when the R/W size is more than 1 byte, these
functions assume that the register address is incremented and handle the
cache accordingly.

Convert FIFO R/W functions to use the regmap _noinc_ versions in order to
remove the manual cache control which was a workaround when using the
_raw_ versions. FIFO registers are properly declared as volatile so
cache will not be used/updated for FIFO accesses.

The Linux kernel CVE team has assigned CVE-2023-52488 to this issue.

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

	Issue introduced in 3.16 with commit dfeae619d781 and fixed in 5.10.215 with commit 4e37416e4ee1
	Issue introduced in 3.16 with commit dfeae619d781 and fixed in 5.15.154 with commit e635f652696e
	Issue introduced in 3.16 with commit dfeae619d781 and fixed in 6.1.76 with commit 416b10d2817c
	Issue introduced in 3.16 with commit dfeae619d781 and fixed in 6.6.15 with commit 084c24e788d9
	Issue introduced in 3.16 with commit dfeae619d781 and fixed in 6.7.3 with commit aa7cb4787698
	Issue introduced in 3.16 with commit dfeae619d781 and fixed in 6.8 with commit dbf4ab821804

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-2023-52488
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/tty/serial/sc16is7xx.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/4e37416e4ee1b1bc17364a68973e0c63be89e611
	https://git.kernel.org/stable/c/e635f652696ef6f1230621cfd89c350cb5ec6169
	https://git.kernel.org/stable/c/416b10d2817c94db86829fb92ad43ce7d002c573
	https://git.kernel.org/stable/c/084c24e788d9cf29c55564de368bf5284f2bb5db
	https://git.kernel.org/stable/c/aa7cb4787698add9367b19f7afc667662c9bdb23
	https://git.kernel.org/stable/c/dbf4ab821804df071c8b566d9813083125e6d97b