CVE-2024-41012

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().