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.