ionic: catch NULL pointer issue on reconfig

It's possible that the driver will dereference a qcq that doesn't exist
when calling ionic_reconfigure_queues(), which causes a page fault BUG.

If a reduction in the number of queues is followed by a different
reconfig such as changing the ring size, the driver can hit a NULL
pointer when trying to clean up non-existent queues.

Fix this by checking to make sure both the qcqs array and qcq entry
exists bofore trying to use and free the entry.

Fixes: 101b40a ("ionic: change queue count with no reset")
Signed-off-by: Brett Creeley <[email protected]>
Signed-off-by: Shannon Nelson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

drivers/net/ethernet/pensando/ionic/ionic_lif.c

@@ -2817,11 +2817,15 @@ int ionic_reconfigure_queues(struct ionic_lif *lif,
 	 * than the full array, but leave the qcq shells in place
 	 */
 	for (i = lif->nxqs; i < lif->ionic->ntxqs_per_lif; i++) {
-		lif->txqcqs[i]->flags &= ~IONIC_QCQ_F_INTR;
-		ionic_qcq_free(lif, lif->txqcqs[i]);
+		if (lif->txqcqs && lif->txqcqs[i]) {
+			lif->txqcqs[i]->flags &= ~IONIC_QCQ_F_INTR;
+			ionic_qcq_free(lif, lif->txqcqs[i]);
+		}
 
-		lif->rxqcqs[i]->flags &= ~IONIC_QCQ_F_INTR;
-		ionic_qcq_free(lif, lif->rxqcqs[i]);
+		if (lif->rxqcqs && lif->rxqcqs[i]) {
+			lif->rxqcqs[i]->flags &= ~IONIC_QCQ_F_INTR;
+			ionic_qcq_free(lif, lif->rxqcqs[i]);
+		}
 	}
 
 	if (err)