CVE-2026-89585: auxdisplay: charlcd: cancel backlight work on registration failure

CVE-2026-89585: auxdisplay: charlcd: cancel backlight work on registration failure

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

auxdisplay: charlcd: cancel backlight work on registration failure

With CONFIG_CHARLCD_BL_FLASH, charlcd_init() schedules bl_work before
charlcd_register() calls misc_register(). If registration fails, the
caller frees the charlcd object while delayed work still contains its
address.

Add charlcd_deinit() to cancel the delayed work and turn the backlight
off. Use it for both registration rollback and normal unregistration.

The Linux kernel CVE team has assigned CVE-2026-89585 to this issue.


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

	Issue introduced in 4.12 with commit 39f8ea46724efbed3ca021863a22337c31be264c and fixed in 6.12.109 with commit fe7ba73dde94c5f413b1588cd444b49105015dda
	Issue introduced in 4.12 with commit 39f8ea46724efbed3ca021863a22337c31be264c and fixed in 6.18.50 with commit 84858671842ae5857b9ed1202b62f9045373dcd1
	Issue introduced in 4.12 with commit 39f8ea46724efbed3ca021863a22337c31be264c and fixed in 7.2.4 with commit ff2fb3c1e60cb247ea3e28c0ea0bea81c18f7755
	Issue introduced in 4.12 with commit 39f8ea46724efbed3ca021863a22337c31be264c and fixed in 7.3-rc1 with commit e3e3bf40916c1e810df03958cfa7ba6883cdce79

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-2026-89585
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/auxdisplay/charlcd.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/fe7ba73dde94c5f413b1588cd444b49105015dda
	https://git.kernel.org/stable/c/84858671842ae5857b9ed1202b62f9045373dcd1
	https://git.kernel.org/stable/c/ff2fb3c1e60cb247ea3e28c0ea0bea81c18f7755
	https://git.kernel.org/stable/c/e3e3bf40916c1e810df03958cfa7ba6883cdce79