cachefiles: wait for ondemand_object_worker to finish when dropping object

Summary

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.

Timeline

1. Jul 29, 2024, 2:32 PM UTCCVE published
2. Sep 10, 2024, 4:22 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Aug 5, 2026, 11:35 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 6.1.95 · fixed in 6.1.100; From 6.6.35 · fixed in 6.6.41

• Linux Linux

  6.8

References 4