CVE-2026-68293: net/mlx5: Fix MCIA register buffer overflow on 32 dword reads

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

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

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

net/mlx5: Fix MCIA register buffer overflow on 32 dword reads

The MCIA register can return up to 32 dwords (128 bytes) when the device
advertises the mcia_32dwords capability, but struct
mlx5_ifc_mcia_reg_bits only defines dword_0..11, leaving room for just
12 dwords (48 bytes) of data.

mlx5_query_mcia() clamps the read size to mlx5_mcia_max_bytes() and then
memcpy()s that many bytes out of the register, potentially reading past
the end of the 'out' buffer. On kernels built with FORTIFY_SOURCE this
is caught as a buffer overflow while reading the module EEPROM via
ethtool:

  detected buffer overflow in memcpy
  kernel BUG at lib/string_helpers.c:1048!
  RIP: 0010:fortify_panic+0x13/0x20
  Call Trace:
   mlx5_query_mcia.isra.0+0x200/0x210 [mlx5_core]
   mlx5_query_module_eeprom_by_page+0x4a/0xa0 [mlx5_core]
   mlx5e_get_module_eeprom_by_page+0xbb/0x120 [mlx5_core]
   eeprom_prepare_data+0xf3/0x170
   ethnl_default_doit+0xf1/0x3b0

Extend the mcia_reg layout to 32 dwords.

The Linux kernel CVE team has assigned CVE-2026-68293 to this issue.


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

	Issue introduced in 5.18 with commit 271907ee2f29cd1078fd219f0778fd824fb1971c and fixed in 6.12.101 with commit 5be4eebd5a3a198dab0adcd550e1cadca79bdfed
	Issue introduced in 5.18 with commit 271907ee2f29cd1078fd219f0778fd824fb1971c and fixed in 6.18.42 with commit 87b39a8c875ca744b7de69af0a8ef8874cffccf1
	Issue introduced in 5.18 with commit 271907ee2f29cd1078fd219f0778fd824fb1971c and fixed in 7.1.6 with commit 88b2a16ddac3357e3f1d528e758b51e2c945d546
	Issue introduced in 5.18 with commit 271907ee2f29cd1078fd219f0778fd824fb1971c and fixed in 7.2-rc5 with commit 11c057d23465c7a5817a7284c896d19d54c0b616

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-2026-68293
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/net/ethernet/mellanox/mlx5/core/port.c
	include/linux/mlx5/mlx5_ifc.h


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/5be4eebd5a3a198dab0adcd550e1cadca79bdfed
	https://git.kernel.org/stable/c/87b39a8c875ca744b7de69af0a8ef8874cffccf1
	https://git.kernel.org/stable/c/88b2a16ddac3357e3f1d528e758b51e2c945d546
	https://git.kernel.org/stable/c/11c057d23465c7a5817a7284c896d19d54c0b616