CVE-2024-41051

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

cachefiles: wait for ondemandobjectworker to finish when dropping object

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

process A processs B process C process D

cachefilesondemandsend_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 cachefilesputobject() // object will be freed cachefilesondemanddeinitobjinfo() kmemcachefree(object) // both info and object are freed ondemandobjectworker()

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