CVE-2026-64083: hwmon: (pmbus/adm1266) reject short block-read responses in the GPIO accessors

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

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

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

hwmon: (pmbus/adm1266) reject short block-read responses in the GPIO accessors

adm1266_gpio_get() and adm1266_gpio_get_multiple() both compose the
pin-status word as

	pins_status = read_buf[0] + (read_buf[1] << 8);

right after i2c_smbus_read_block_data(), guarding only against an
error return.  A well-behaved device returns 2 bytes for
GPIO_STATUS/PDIO_STATUS, but the helper happily reports a 0- or
1-byte response too.  If the device returns 0 bytes, both read_buf
slots are uninitialized stack memory; if it returns 1 byte, read_buf[1]
is.

The composed value then flows through set_bit() into the caller's
*bits in adm1266_gpio_get_multiple(), or into the return value of
adm1266_gpio_get(), and ends up in userspace via gpiolib (sysfs and
the char-dev ioctls).  That leaks a few bits of kernel stack per
request on any device whose firmware glitch, bus error, or hostile
slave produces a short block-read response.

Add the missing length check to both call sites and surface a short
response as -EIO.

The Linux kernel CVE team has assigned CVE-2026-64083 to this issue.


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

	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 5.10.258 with commit fd9196aad9e5a3845cea17de3405ebc700382142
	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 5.15.209 with commit ee4799becf7d2af3778007e22c2e55c4009a49c7
	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 6.1.175 with commit c603b6c6840ac0c6285f5eefea0de6242710af21
	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 6.6.142 with commit a2d1c819348b36fccbbfcf37c5fa7a50a9b4528f
	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 6.12.92 with commit ae25cf2ea9ebd06d7ad416647dbdc7b5d0172946
	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 6.18.34 with commit eb3cd9bb590460c6127145cb245be925d23f5232
	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 7.0.11 with commit 64fa9328948ddcc0f7f3c23ea1756c126d9dffac
	Issue introduced in 5.10 with commit d98dfad35c38c037b37c4adc99df01da571031a5 and fixed in 7.1 with commit a7232f68c43ca62f545049b7f5fbfc75137b843b

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-2026-64083
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/pmbus/adm1266.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/fd9196aad9e5a3845cea17de3405ebc700382142
	https://git.kernel.org/stable/c/ee4799becf7d2af3778007e22c2e55c4009a49c7
	https://git.kernel.org/stable/c/c603b6c6840ac0c6285f5eefea0de6242710af21
	https://git.kernel.org/stable/c/a2d1c819348b36fccbbfcf37c5fa7a50a9b4528f
	https://git.kernel.org/stable/c/ae25cf2ea9ebd06d7ad416647dbdc7b5d0172946
	https://git.kernel.org/stable/c/eb3cd9bb590460c6127145cb245be925d23f5232
	https://git.kernel.org/stable/c/64fa9328948ddcc0f7f3c23ea1756c126d9dffac
	https://git.kernel.org/stable/c/a7232f68c43ca62f545049b7f5fbfc75137b843b