Subject: CVE-2024-50058: serial: protect uart_port_dtr_rts() in uart_shutdown() too

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

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

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

serial: protect uart_port_dtr_rts() in uart_shutdown() too

Commit af224ca2df29 (serial: core: Prevent unsafe uart port access, part
3) added few uport == NULL checks. It added one to uart_shutdown(), so
the commit assumes, uport can be NULL in there. But right after that
protection, there is an unprotected "uart_port_dtr_rts(uport, false);"
call. That is invoked only if HUPCL is set, so I assume that is the
reason why we do not see lots of these reports.

Or it cannot be NULL at this point at all for some reason :P.

Until the above is investigated, stay on the safe side and move this
dereference to the if too.

I got this inconsistency from Coverity under CID 1585130. Thanks.

The Linux kernel CVE team has assigned CVE-2024-50058 to this issue.

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

	Fixed in 6.6.57 with commit e418d91195d2
	Fixed in 6.11.4 with commit 76ed24a34223
	Fixed in 6.12-rc1 with commit 602babaa84d6

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-2024-50058
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/serial_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/e418d91195d29d5f9c9685ff309b92b04b41dc40
	https://git.kernel.org/stable/c/76ed24a34223bb2c6b6162e1d8389ec4e602a290
	https://git.kernel.org/stable/c/602babaa84d627923713acaf5f7e9a4369e77473