Heap Overflow in Linux Kernel USB Serial Driver

Detection Guidance

This vulnerability involves a heap overflow in the Linux kernel's USB serial driver (io_ti) when reading manufacturer information from a USB device's I2C EEPROM. Detection involves identifying if the system is running a vulnerable version of the Linux kernel with the io_ti driver.

Since the vulnerability is triggered by plugging in a malicious USB device, monitoring USB device connections and checking kernel logs for unusual errors related to the io_ti driver can help detect exploitation attempts.

Suggested commands to help detect or investigate this vulnerability include:

• Check the kernel version to determine if it includes the fix: `uname -r`
• List loaded USB serial drivers and check for io_ti: `lsmod | grep io_ti`
• Monitor kernel logs for errors related to USB serial devices: `dmesg | grep -i usb` or `journalctl -k | grep io_ti`
• Use `lsusb` to list connected USB devices and identify suspicious or unknown devices.

Note that there are no specific detection commands or signatures provided in the available information.

Useful 0 Not Useful 0

Executive Summary

This vulnerability exists in the Linux kernel's USB serial driver for Texas Instruments devices (io_ti). The function get_manuf_info() reads data from a device's I2C EEPROM into a buffer that is only 10 bytes in size. However, the size of the data to be read is controlled by a field called Size, which comes from the device itself and can be as large as 16377 bytes. Because the code only checks that Size is less than a maximum limit (16384 bytes) but does not verify it against the actual buffer size, a malicious USB device can cause a heap overflow by specifying a large Size value. This overflow can be up to 16367 bytes, potentially overwriting memory beyond the allocated buffer.

Additionally, another function, valid_csum(), iterates over the buffer using the same unchecked Size value, which compounds the out-of-bounds memory access. The vulnerability was fixed by adding validation to reject descriptors with unexpected lengths before reading the data.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can allow a malicious USB device to cause a heap overflow in the Linux kernel when plugged into a host system. Such a heap overflow can lead to memory corruption, which attackers might exploit to execute arbitrary code with kernel privileges, cause system crashes, or escalate their privileges on the affected system.

Useful 0 Not Useful 0

Mitigation Strategies

To mitigate this vulnerability, ensure that your Linux kernel is updated to a version where the fix for the heap overflow in the io_ti USB serial driver has been applied.

The fix involves rejecting descriptors with unexpected length before reading from the device EEPROM, preventing heap overflow caused by malicious USB devices.

As an immediate step, avoid connecting untrusted or unknown USB devices that use the affected driver until the kernel is patched.

Useful 0 Not Useful 0