Subject: CVE-2024-43893: serial: core: check uartclk for zero to avoid divide by zero

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

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

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

serial: core: check uartclk for zero to avoid divide by zero

Calling ioctl TIOCSSERIAL with an invalid baud_base can
result in uartclk being zero, which will result in a
divide by zero error in uart_get_divisor(). The check for
uartclk being zero in uart_set_info() needs to be done
before other settings are made as subsequent calls to
ioctl TIOCSSERIAL for the same port would be impacted if
the uartclk check was done where uartclk gets set.

Oops: divide error: 0000  PREEMPT SMP KASAN PTI
RIP: 0010:uart_get_divisor (drivers/tty/serial/serial_core.c:580)
Call Trace:
 <TASK>
serial8250_get_divisor (drivers/tty/serial/8250/8250_port.c:2576
    drivers/tty/serial/8250/8250_port.c:2589)
serial8250_do_set_termios (drivers/tty/serial/8250/8250_port.c:502
    drivers/tty/serial/8250/8250_port.c:2741)
serial8250_set_termios (drivers/tty/serial/8250/8250_port.c:2862)
uart_change_line_settings (./include/linux/spinlock.h:376
    ./include/linux/serial_core.h:608 drivers/tty/serial/serial_core.c:222)
uart_port_startup (drivers/tty/serial/serial_core.c:342)
uart_startup (drivers/tty/serial/serial_core.c:368)
uart_set_info (drivers/tty/serial/serial_core.c:1034)
uart_set_info_user (drivers/tty/serial/serial_core.c:1059)
tty_set_serial (drivers/tty/tty_io.c:2637)
tty_ioctl (drivers/tty/tty_io.c:2647 drivers/tty/tty_io.c:2791)
__x64_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:907
    fs/ioctl.c:893 fs/ioctl.c:893)
do_syscall_64 (arch/x86/entry/common.c:52
    (discriminator 1) arch/x86/entry/common.c:83 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Rule: add

The Linux kernel CVE team has assigned CVE-2024-43893 to this issue.

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

	Fixed in 4.19.320 with commit 3bbd90fca824
	Fixed in 5.4.282 with commit 55b2a5d331a6
	Fixed in 5.10.224 with commit 52b138f10211
	Fixed in 5.15.165 with commit 9196e42a3b8e
	Fixed in 6.1.105 with commit e13ba3fe5ee0
	Fixed in 6.6.46 with commit e3ad50387628
	Fixed in 6.10.5 with commit 68dc02f319b9
	Fixed in 6.11 with commit 6eabce6608d6

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-2024-43893
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/3bbd90fca824e6fd61fb20f6dd2b0fa5f8b14bba
	https://git.kernel.org/stable/c/55b2a5d331a6ceb1c4372945fdb77181265ba24f
	https://git.kernel.org/stable/c/52b138f1021113e593ee6ad258ce08fe90693a9e
	https://git.kernel.org/stable/c/9196e42a3b8eeff1707e6ef769112b4b6096be49
	https://git.kernel.org/stable/c/e13ba3fe5ee070f8a9dab60029d52b1f61da5051
	https://git.kernel.org/stable/c/e3ad503876283ac3fcca922a1bf243ef9eb0b0e2
	https://git.kernel.org/stable/c/68dc02f319b9ee54dc23caba742a5c754d1cccc8
	https://git.kernel.org/stable/c/6eabce6608d6f3440f4c03aa3d3ef50a47a3d193