Linux Kernel IPv6 Module Improper Symbol Export Vulnerability

A vulnerability has been identified in the Linux kernel's IPv6 module related to the improper export of a function initialized with the __init annotation. This issue arises because the .init.text section, where such functions are placed, is cleared after initialization, leaving modules unable to access these symbols. Attempting to use a freed symbol can lead to a kernel panic. The problem was detected in linux-next builds after the modpost tool, which identifies such issues, was repaired. The vulnerability exists because the function seg6_hmac_init() was exported while still being marked for initialization, creating a conflict. The issue can be resolved by either removing the __init annotation or the EXPORT_SYMBOL directive. In this case, the latter was chosen since both the caller and callee belong to the same module, making it an internal function call.

Impact

Accessing a freed symbol can cause a kernel panic, leading to a system crash.