CVE-2025-40189

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.