Linux Kernel up to 6.9.8 filelock fcntl_setlk use after free

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.9.8 and classified as critical. This vulnerability affects the function fcntl_setlk of the component filelock. This manipulation causes use after free. This vulnerability is registered as CVE-2024-41012. Furthermore, an exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.9.8. It has been declared as critical. Affected by this vulnerability is the function fcntl_setlk of the component filelock. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: filelock: Remove locks reliably when fcntl/close race is detected When fcntl_setlk() races with close(), it removes the created lock with do_lock_file_wait(). However, LSMs can allow the first do_lock_file_wait() that created the lock while denying the second do_lock_file_wait() that tries to remove the lock. Separately, posix_lock_file() could also fail to remove a lock due to GFP_KERNEL allocation failure (when splitting a range in the middle). After the bug has been triggered, use-after-free reads will occur in lock_get_status() when userspace reads /proc/locks. This can likely be used to read arbitrary kernel memory, but can't corrupt kernel memory. Fix it by calling locks_remove_posix() instead, which is designed to reliably get rid of POSIX locks associated with the given file and files_struct and is also used by filp_flush().

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2024-41012 since 07/12/2024. The exploitation appears to be difficult. Technical details and also a public exploit are known.

It is possible to download the exploit at packetstormsecurity.com. It is declared as proof-of-concept. The vulnerability scanner Nessus provides a plugin with the ID 207773 (Oracle Linux 8 : kernel (ELSA-2024-7000)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.9.9 eliminates this vulnerability. Applying the patch b6d223942c34/3cad1bc01041 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (207773). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.9.0
• 6.9.1
• 6.9.2
• 6.9.3
• 6.9.4
• 6.9.5
• 6.9.6
• 6.9.7
• 6.9.8

License

• open-source

Website

• Vendor: https://www.kernel.org/

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