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.