In the Linux kernel, the following vulnerability has been resolved: padata: avoid UAF for...

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

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.