In the Linux kernel, the following vulnerability has been resolved:

netfs: Delete subtree of fs/netfs when netfs module exits

In netfs_init() or fscache_proc_init(), we create dentry under fs/netfs, but in netfs_exit(), we only delete the proc entry of fs/netfs without deleting its subtree. This triggers the following WARNING:

================================================================== remove_proc_entry: removing non-empty directory fs/netfs, leaking at least requests WARNING: CPU: 4 PID: 566 at fs/proc/generic.c:717 remove_proc_entry+0x160/0x1c0 Modules linked in: netfs(-) CPU: 4 UID: 0 PID: 566 Comm: rmmod Not tainted 6.11.0-rc3 #860 RIP: 0010:remove_proc_entry+0x160/0x1c0 Call Trace: netfs_exit+0x12/0x620 [netfs] __do_sys_delete_module.isra.0+0x14c/0x2e0 do_syscall_64+0x4b/0x110 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Therefore use remove_proc_subtree() instead of remove_proc_entry() to fix the above problem.

Weakness

The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, languages such as Java, Ruby, and Lisp perform automatic garbage collection that releases memory for objects that have been deallocated.
• Use resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems.
• When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged users; alternately, begin releasing resources for less-privileged users. While this mitigation may protect the system from attack, it will not necessarily stop attackers from adversely impacting other users.
• Ensure that the application performs the appropriate error checks and error handling in case resources become unavailable (CWE-703).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/469.html

References

• https://git.kernel.org/stable/c/3c58a9575e02c2b90a3180007d57105ceaa7c246
• https://git.kernel.org/stable/c/603f95cefbee06a31b03137b777f03e3c2163d72
• https://git.kernel.org/stable/c/7a9eaf97d56625e55b31a7beb558e1ee185ca461