Subject: CVE-2024-46706: tty: serial: fsl_lpuart: mark last busy before uart_add_one_port

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

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

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

tty: serial: fsl_lpuart: mark last busy before uart_add_one_port

With "earlycon initcall_debug=1 loglevel=8" in bootargs, kernel
sometimes boot hang. It is because normal console still is not ready,
but runtime suspend is called, so early console putchar will hang
in waiting TRDE set in UARTSTAT.

The lpuart driver has auto suspend delay set to 3000ms, but during
uart_add_one_port, a child device serial ctrl will added and probed with
its pm runtime enabled(see serial_ctrl.c).
The runtime suspend call path is:
device_add
     |-> bus_probe_device
           |->device_initial_probe
	           |->__device_attach
                         |-> pm_runtime_get_sync(dev->parent);
			 |-> pm_request_idle(dev);
			 |-> pm_runtime_put(dev->parent);

So in the end, before normal console ready, the lpuart get runtime
suspended. And earlycon putchar will hang.

To address the issue, mark last busy just after pm_runtime_enable,
three seconds is long enough to switch from bootconsole to normal
console.

The Linux kernel CVE team has assigned CVE-2024-46706 to this issue.

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

	Issue introduced in 6.2 with commit 43543e6f539b and fixed in 6.6.48 with commit 8eb92cfca6c2
	Issue introduced in 6.2 with commit 43543e6f539b and fixed in 6.10.7 with commit 3ecf625d4acb
	Issue introduced in 6.2 with commit 43543e6f539b and fixed in 6.11 with commit dc98d76a15bc

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-2024-46706
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/fsl_lpuart.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/8eb92cfca6c2c5a15ab1773f3d18ab8d8f7dbb68
	https://git.kernel.org/stable/c/3ecf625d4acb71d726bc0b49403cf68388b3d58d
	https://git.kernel.org/stable/c/dc98d76a15bc29a9a4e76f2f65f39f3e590fb15c