CVE-2026-80580: fbdev: bound mode sysfs output to the sysfs buffer

CVE-2026-80580: fbdev: bound mode sysfs output to the sysfs buffer

[Greg Kroah-Hartman]

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

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

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

fbdev: bound mode sysfs output to the sysfs buffer

mode_string() uses snprintf() which can return a value larger than the
remaining buffer space. show_modes() accumulates the return value into i
without checking whether i has reached PAGE_SIZE, causing the offset to
advance past the sysfs buffer if the modelist is long enough.

Add a size parameter to mode_string() and use scnprintf() to return
only the bytes actually written. Add an early return when offset
already exceeds the buffer. In show_modes(), stop accumulating once
the buffer is full.

The Linux kernel CVE team has assigned CVE-2026-80580 to this issue.


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

	Fixed in 7.1.10 with commit 873a1aa15c313263f2e18b38cf525623cc4fabf6
	Fixed in 7.2 with commit d15d51fb26e830af58f3f21964f1c09c239077ea

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-2026-80580
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/video/fbdev/core/fbsysfs.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/873a1aa15c313263f2e18b38cf525623cc4fabf6
	https://git.kernel.org/stable/c/d15d51fb26e830af58f3f21964f1c09c239077ea