CVE-2026-74685: hwmon: (ltc4282) Clamp negative current limits

CVE-2026-74685: hwmon: (ltc4282) Clamp negative current limits

[Greg Kroah-Hartman]

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

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

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

hwmon: (ltc4282) Clamp negative current limits

When a negative value is passed to ltc4282_write_curr(), the signed long
val is cast directly to u64:

drivers/hwmon/ltc4282.c:ltc4282_write_curr() {
        /* need to pass it in millivolt */
        u32 in = DIV_ROUND_CLOSEST_ULL((u64)val * st->rsense, DECA * MICRO);
        ...
}

This cast converts negative inputs into large positive values. The
subsequent division result overflows the u32 in variable, truncating
to a pseudo-random positive value. When this is passed to
ltc4282_write_voltage_byte(), it is clamped to the maximum limit instead
of zero.

Clamp val to 0 and to the maximum supported upper limit before the cast
and assign the result to a 64-bit temporary variable before the division
to avoid the underflow and an also possible overflow.

The Linux kernel CVE team has assigned CVE-2026-74685 to this issue.


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

	Issue introduced in 6.9 with commit cbc29538dbf7d7400f1ffc5dd5713e6a551463a0 and fixed in 6.12.104 with commit 60e06c4dba696173982393252a40ceb7dd2eec18
	Issue introduced in 6.9 with commit cbc29538dbf7d7400f1ffc5dd5713e6a551463a0 and fixed in 6.18.45 with commit de58b90a4d1417c15b693eb04c0ce6bc925d84c6
	Issue introduced in 6.9 with commit cbc29538dbf7d7400f1ffc5dd5713e6a551463a0 and fixed in 7.1.9 with commit 046e56b53c09375ef39903514496aa5508db9729
	Issue introduced in 6.9 with commit cbc29538dbf7d7400f1ffc5dd5713e6a551463a0 and fixed in 7.2 with commit e253dd5f9f6d875a317895bf43ec9534ed7523cb

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-2026-74685
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/hwmon/ltc4282.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/60e06c4dba696173982393252a40ceb7dd2eec18
	https://git.kernel.org/stable/c/de58b90a4d1417c15b693eb04c0ce6bc925d84c6
	https://git.kernel.org/stable/c/046e56b53c09375ef39903514496aa5508db9729
	https://git.kernel.org/stable/c/e253dd5f9f6d875a317895bf43ec9534ed7523cb