CVE-2024-41051

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

cachefiles: wait for ondemand_object_worker to finish when dropping object

When queuing ondemand_object_worker() to re-open the object, cachefiles_object is not pinned. The cachefiles_object may be freed when the pending read request is completed intentionally and the related erofs is umounted. If ondemand_object_worker() runs after the object is freed, it will incur use-after-free problem as shown below.

process A processs B process C process D

cachefiles_ondemand_send_req() // send a read req X // wait for its completion

       // close ondemand fd
       cachefiles_ondemand_fd_release()
       // set object as CLOSE

                   cachefiles_ondemand_daemon_read()
                   // set object as REOPENING
                   queue_work(fscache_wq, &info->ondemand_work)

                            // close /dev/cachefiles
                            cachefiles_daemon_release
                            cachefiles_flush_reqs
                            complete(&req->done)

// read req X is completed // umount the erofs fs cachefiles_put_object() // object will be freed cachefiles_ondemand_deinit_obj_info() kmem_cache_free(object) // both info and object are freed ondemand_object_worker()

When dropping an object, it is no longer necessary to reopen the object, so use cancel_work_sync() to cancel or wait for ondemand_object_worker() to finish.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/12e009d60852f7bce0afc373ca0b320f14150418
• https://git.kernel.org/stable/c/b26525b2183632f16a3a4108fe6a4bfa8afac6ed
• https://git.kernel.org/stable/c/d3179bae72b1b5e555ba839d6d9f40a350a4d78a
• https://git.kernel.org/stable/c/ec9289369259d982e735a71437e32e6b4035290c
• https://git.kernel.org/stable/c/12e009d60852f7bce0afc373ca0b320f14150418
• https://git.kernel.org/stable/c/b26525b2183632f16a3a4108fe6a4bfa8afac6ed
• https://git.kernel.org/stable/c/d3179bae72b1b5e555ba839d6d9f40a350a4d78a
• https://git.kernel.org/stable/c/ec9289369259d982e735a71437e32e6b4035290c
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html