CVE-2025-21726: Use After Free

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

padata: avoid UAF for reorder_work

Although the previous patch can avoid ps and ps UAF for _do_serial, it can not avoid potential UAF issue for reorder_work. This issue can happen just as below:

crypto_request crypto_request crypto_del_alg padata_do_serial ... padata_reorder // processes all remaining // requests then breaks while (1) { if (!padata) break; ... }

padata_do_serial // new request added list_add // sees the new request queue_work(reorder_work) padata_reorder queue_work_on(squeue->work) ...

<kworker context> padata_serial_worker // completes new request, // no more outstanding // requests

crypto_del_alg // free pd

<kworker context> invoke_padata_reorder // UAF of pd

To avoid UAF for 'reorder_work', get 'pd' ref before put 'reorder_work' into the 'serial_wq' and put 'pd' ref until the 'serial_wq' finish.