linux-cve-announce - CVE-2025-40189: net: usb: lan78xx: Fix lost EEPROM read timeout error(-ETIMEDOUT) in lan78xx_read_raw

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Message-ID: <2025111244-CVE-2025-40189-c4ca@gregkh>
Date: Wed, 12 Nov 2025 17:00:52 -0500
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40189: net: usb: lan78xx: Fix lost EEPROM read timeout error(-ETIMEDOUT) in lan78xx_read_raw_eeprom

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

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

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

net: usb: lan78xx: Fix lost EEPROM read timeout error(-ETIMEDOUT) in lan78xx_read_raw_eeprom

Syzbot reported read of uninitialized variable BUG with following call stack.

lan78xx 8-1:1.0 (unnamed net_device) (uninitialized): EEPROM read operation timeout
=====================================================
BUG: KMSAN: uninit-value in lan78xx_read_eeprom drivers/net/usb/lan78xx.c:1095 [inline]
BUG: KMSAN: uninit-value in lan78xx_init_mac_address drivers/net/usb/lan78xx.c:1937 [inline]
BUG: KMSAN: uninit-value in lan78xx_reset+0x999/0x2cd0 drivers/net/usb/lan78xx.c:3241
 lan78xx_read_eeprom drivers/net/usb/lan78xx.c:1095 [inline]
 lan78xx_init_mac_address drivers/net/usb/lan78xx.c:1937 [inline]
 lan78xx_reset+0x999/0x2cd0 drivers/net/usb/lan78xx.c:3241
 lan78xx_bind+0x711/0x1690 drivers/net/usb/lan78xx.c:3766
 lan78xx_probe+0x225c/0x3310 drivers/net/usb/lan78xx.c:4707

Local variable sig.i.i created at:
 lan78xx_read_eeprom drivers/net/usb/lan78xx.c:1092 [inline]
 lan78xx_init_mac_address drivers/net/usb/lan78xx.c:1937 [inline]
 lan78xx_reset+0x77e/0x2cd0 drivers/net/usb/lan78xx.c:3241
 lan78xx_bind+0x711/0x1690 drivers/net/usb/lan78xx.c:3766

The function lan78xx_read_raw_eeprom failed to properly propagate EEPROM
read timeout errors (-ETIMEDOUT). In the fallthrough path, it first
attempted to restore the pin configuration for LED outputs and then
returned only the status of that restore operation, discarding the
original timeout error.

As a result, callers could mistakenly treat the data buffer as valid
even though the EEPROM read had actually timed out with no data or partial
data.

To fix this, handle errors in restoring the LED pin configuration separately.
If the restore succeeds, return any prior EEPROM timeout error correctly
to the caller.

The Linux kernel CVE team has assigned CVE-2025-40189 to this issue.


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

	Issue introduced in 6.14 with commit 8b1b2ca83b200fa46fdfb81e80ad5fe34537e6d4 and fixed in 6.17.4 with commit a72a7c4f675080a324d4c2167bd2314d968279f1
	Issue introduced in 6.14 with commit 8b1b2ca83b200fa46fdfb81e80ad5fe34537e6d4 and fixed in 6.18-rc1 with commit 49bdb63ff64469a6de8ea901aef123c75be9bbe7

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-2025-40189
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/usb/lan78xx.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/a72a7c4f675080a324d4c2167bd2314d968279f1
	https://git.kernel.org/stable/c/49bdb63ff64469a6de8ea901aef123c75be9bbe7