CVE-2025-40189: net: usb: lan78xx: Fix lost EEPROM read timeout error(-ETIMEDOUT) in lan78xx_read_raw_eeprom
In the Linux kernel, the following vulnerability has been resolved:
net: usb: lan78xx: Fix lost EEPROM read timeout error(-ETIMEDOUT) in lan78xxreadraweeprom
Syzbot reported read of uninitialized variable BUG with following call stack.
lan78xx 8-1:1.0 (unnamed netdevice) (uninitialized): EEPROM read operation timeout ===================================================== BUG: KMSAN: uninit-value in lan78xxreadeeprom drivers/net/usb/lan78xx.c:1095 [inline] BUG: KMSAN: uninit-value in lan78xxinitmacaddress drivers/net/usb/lan78xx.c:1937 [inline] BUG: KMSAN: uninit-value in lan78xxreset+0x999/0x2cd0 drivers/net/usb/lan78xx.c:3241 lan78xxreadeeprom drivers/net/usb/lan78xx.c:1095 [inline] lan78xxinitmacaddress drivers/net/usb/lan78xx.c:1937 [inline] lan78xxreset+0x999/0x2cd0 drivers/net/usb/lan78xx.c:3241 lan78xxbind+0x711/0x1690 drivers/net/usb/lan78xx.c:3766 lan78xxprobe+0x225c/0x3310 drivers/net/usb/lan78xx.c:4707
Local variable sig.i.i created at: lan78xxreadeeprom drivers/net/usb/lan78xx.c:1092 [inline] lan78xxinitmacaddress drivers/net/usb/lan78xx.c:1937 [inline] lan78xxreset+0x77e/0x2cd0 drivers/net/usb/lan78xx.c:3241 lan78xxbind+0x711/0x1690 drivers/net/usb/lan78xx.c:3766
The function lan78xxreadraweeprom 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.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2025-40189?
CVE-2025-40189 has been categorized as a moderate severity vulnerability in the Linux kernel.
How do I fix CVE-2025-40189?
To fix CVE-2025-40189, update your Linux kernel to the latest stable version that includes the patch for this vulnerability.
What is the impact of CVE-2025-40189?
CVE-2025-40189 may result in issues related to lost EEPROM read timeout errors in affected devices.
What component of the system is affected by CVE-2025-40189?
CVE-2025-40189 affects the net subsystem related to USB devices in the Linux kernel.
Who reported the vulnerability in CVE-2025-40189?
The vulnerability associated with CVE-2025-40189 was reported by Syzbot.