[PATCH 04/33] 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.

Fixes: 68ca949cdb04 ("[SCSI] qla2xxx: Add CPU affinity support.")
Reported-by: Sashiko <[email protected]>
Cc: [email protected]
Signed-off-by: Nilesh Javali <[email protected]>
---
 drivers/scsi/qla2xxx/qla_mid.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/scsi/qla2xxx/qla_mid.c b/drivers/scsi/qla2xxx/qla_mid.c
index b7d9c1a53f3c..33bfc61d8165 100644
--- a/drivers/scsi/qla2xxx/qla_mid.c
+++ b/drivers/scsi/qla2xxx/qla_mid.c
@@ -606,6 +606,10 @@ qla25xx_free_rsp_que(struct scsi_qla_host *vha, struct rsp_que *rsp)
 		rsp->msix->handle = NULL;
 	}
 
+	/* Flush any queued response work before freeing the queue/qpair. */
+	if (rsp->qpair && ha->wq)
+		cancel_work_sync(&rsp->qpair->q_work);
+
 	if (rsp->ring)
 		dma_free_coherent(&ha->pdev->dev,
 				  (rsp->length + 1) * rsp_entry_size,
-- 
2.47.3