CVE-2026-64086: hwmon: (pmbus/adm1266) include PEC byte in pmbus_block_xfer read buffer

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

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

hwmon: (pmbus/adm1266) include PEC byte in pmbus_block_xfer read buffer

adm1266_pmbus_block_xfer() sets up the read transaction with

	.buf = data->read_buf,
	.len = ADM1266_PMBUS_BLOCK_MAX + 2,

but read_buf in struct adm1266_data is declared as

	u8 read_buf[ADM1266_PMBUS_BLOCK_MAX + 1];

For a max-length block response (length byte = 255 + up to 1 PEC
byte), the i2c controller is told to write 257 bytes into a 256-byte
buffer, putting one byte past the end of read_buf.  The same response
also makes the subsequent PEC compare

	if (crc != msgs[1].buf[msgs[1].buf[0] + 1])

read a byte beyond the array.

Bump the read_buf declaration to ADM1266_PMBUS_BLOCK_MAX + 2 so the
buffer can hold the length byte, up to 255 payload bytes, and the PEC
byte the i2c_msg length already accounts for.

The Linux kernel CVE team has assigned CVE-2026-64086 to this issue.


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

	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 5.10.258 with commit 397d3f523bfff2f4e3dacf9b1339bd76dc207f78
	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 5.15.209 with commit 472744f69d25a2d5111ad62f1d62579dce2c13c8
	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 6.1.175 with commit 528a9f88e88502d0c2f2052a279415074cd83715
	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 6.6.142 with commit d94ceb16e55b6d8019ab069e357c76ac42f0ffbc
	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 6.12.92 with commit bd5be3fa5de6dbf61f1b3cec6b79c2c2f8065694
	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 6.18.34 with commit 2279c342d94eca225bf9f301c8806a05a1c81619
	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 7.0.11 with commit a6c802145a8de0830bca803c6d415f7e9e683624
	Issue introduced in 5.10 with commit 407dc802a9c0809ca6a48de4b4c63305eb84ef56 and fixed in 7.1 with commit 487566cb1ccdf3756fdd7bf8d875e612ff3169bb

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-2026-64086
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/397d3f523bfff2f4e3dacf9b1339bd76dc207f78
	https://git.kernel.org/stable/c/472744f69d25a2d5111ad62f1d62579dce2c13c8
	https://git.kernel.org/stable/c/528a9f88e88502d0c2f2052a279415074cd83715
	https://git.kernel.org/stable/c/d94ceb16e55b6d8019ab069e357c76ac42f0ffbc
	https://git.kernel.org/stable/c/bd5be3fa5de6dbf61f1b3cec6b79c2c2f8065694
	https://git.kernel.org/stable/c/2279c342d94eca225bf9f301c8806a05a1c81619
	https://git.kernel.org/stable/c/a6c802145a8de0830bca803c6d415f7e9e683624
	https://git.kernel.org/stable/c/487566cb1ccdf3756fdd7bf8d875e612ff3169bb