Welcome to an important update on a recently discovered vulnerability in the Linux Kernel, identified as CVE-2024-50002. As users and advocates of Linux systems, it's crucial to stay informed about potential security issues that could affect the integrity and performance of our systems. Here, we'll break down the details of CVE-2024-50002, its implications, and the remedial measures taken.
What is CVE-2024-50002?
CVE-2024-50002 is categorized under the security vulnerabilities specifically impacting the Linux kernel. It has been assigned a medium severity rating with a score of 5.5. The issue lies within the kernel's handling of module insertions and deletions, particularly when dealing with static calls—a mechanism used for optimizing certain types of indirect function calls.
Description of the Vulnerability:
The core of CVE-2024-50002 revolves around the static_call_del_module() function, which is responsible for cleaning up the entries of static call modules when a module initiation fails. During the module insertion process, static_call_add_module() is triggered to initialize static calls in a module, which in turn calls __static_call_init(). This function attempts to allocate a struct static_call_mod to manage the static call sites within a module.
If the allocation of the struct fails, the function exits with an error, and static_call_del_module() is invoked to clean up. Here lies the vulnerability: if not all keys used by the module have been converted to module chains prior to the failure, static_call_del_module() can cause a #GP (General Protection fault) since it assumes that all key::mods point to a valid structure.
This issue arises because key::mods is part of a union used to save space, which includes both mods and sites pointers. The type of each pointer is distinguished by a specific bit within the union. When static_call_del_module() encounters a pointer not properly set up as a mods pointer due to prior allocation failure, it incorrectly dereferences this pointer, leading to system instability or crashes.
How It Affects Linux Users:
This vulnerability primarily affects systems where new kernel modules are frequently loaded and unloaded, such as systems used for testing or in environments where custom modules are developed.
Resolution:
The fix involves adding checks in the static_call_del_module() function to accurately determine if a pointer is a mods or a sites pointer before dereferencing it. This prevents the incorrect assumption and subsequent mishandling that could lead to system crashes. Users are strongly encouraged to apply updates that incorporate these fixes to ensure system stability and security.
In Conclusion:
CVE-2024-50002 reminds us of the necessity to rigorously monitor and update our Linux systems consistently. By understanding the technical background and impact of such vulnerabilities, users and system administrators can better protect their infrastructure against potential threats. Stay tuned to LinuxPatch for more updates and detailed analyses of Linux security issues.