CVE-2024-41012 Information

Description

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().

Reference

https://git.kernel.org/stable/c/b6d223942c34057fdfd8f149e763fa823731b224 https://git.kernel.org/stable/c/3cad1bc010416c6dd780643476bc59ed742436b9