Linux: scsi: qla2xxx: Fix use-after-free of qpair work on queue teardown

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

scsi: qla2xxx: Fix use-after-free of qpair work on queue teardown

The response queue MSI-X handler qla2xxx_msix_rsp_q() schedules qla_do_work() via queue_work(ha->wq, &qpair->q_work). qla_do_work() dereferences the qpair (vha, rsp) and takes qpair->qp_lock.

During teardown, qla2xxx_delete_qpair() deletes the response queue, which calls free_irq() in qla25xx_free_rsp_que(), and then frees the queue and the qpair. free_irq() waits for running hardirq handlers but does not cancel work already placed on ha->wq. A still-pending q_work then runs qla_do_work() against the freed qpair and response queue, causing a use-after-free. This is especially likely during full adapter teardown, where destroy_workqueue(ha->wq) forces pending work to run after the queue pairs have been freed.

Flush the work item with cancel_work_sync() in qla25xx_free_rsp_que() after free_irq() has released the interrupt (so no new work can be queued) and before the response queue and qpair memory are freed (so the flushed handler still sees valid memory). Guard on rsp->qpair and ha->wq to match the INIT_WORK() condition and avoid operating on an uninitialized work_struct.