Linux Kernel IPVS Uninitialized Stack Access Vulnerability Leading to Undefined Behavior

A vulnerability in the Linux kernel's IP Virtual Server (IPVS) module has been identified, stemming from uninitialized stack access in the function 'ip_vs_protocol_init()'. This issue arises under certain kernel configurations when the kernel is built with Clang/LLVM. The compiler fails to generate a proper return or jump instruction for 'ip_vs_protocol_init()', causing a build-time warning from objtool' that the function falls through to the next one without a proper termination. At runtime, this flaw can lead to a system crash when loading the IPVS module, or a boot-time panic if the module is built into the kernel.

Impact

Exploitation of this vulnerability causes a system crash, either by triggering an 'oops' when loading the IPVS module or a boot-time panic if the module is integrated into the kernel.

Reproduction

The vulnerability can be reproduced by building the Linux kernel with Clang/LLVM under certain configurations that expose the issue. The 'ip_vs_protocol_init()' function will then be improperly compiled, leading to a fall-through behavior that causes an uninitialized stack access. When the IPVS module is loaded, this uninitialized access results in an 'oops' error, or if the module is built into the kernel, a boot-time panic occurs.

Remediation

The vulnerability has been addressed by initializing the stack buffer in the 'ip_vs_protocol_init()' function to prevent undefined behavior. Users should apply the latest patches available in the Linux kernel to mitigate this issue.