s390/qeth: fix use-after-free in error path

BugLink: https://bugs.launchpad.net/bugs/1822271

[ Upstream commit afa0c590 ]

The error path in qeth_alloc_qdio_buffers() that takes care of
cleaning up the Output Queues is buggy. It first frees the queue, but
then calls qeth_clear_outq_buffers() with that very queue struct.

Make the call to qeth_clear_outq_buffers() part of the free action
(in the correct order), and while at it fix the naming of the helper.

Fixes: 0da9581d ("qeth: exploit asynchronous delivery of storage blocks")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/s390/net/qeth_core_main.c

@@ -2460,11 +2460,12 @@ static int qeth_init_qdio_out_buf(struct qeth_qdio_out_q *q, int bidx)
 	return rc;
 }
 
-static void qeth_free_qdio_out_buf(struct qeth_qdio_out_q *q)
+static void qeth_free_output_queue(struct qeth_qdio_out_q *q)
 {
 	if (!q)
 		return;
 
+	qeth_clear_outq_buffers(q, 1);
 	qdio_free_buffers(q->qdio_bufs, QDIO_MAX_BUFFERS_PER_Q);
 	kfree(q);
 }
@@ -2537,10 +2538,8 @@ static int qeth_alloc_qdio_buffers(struct qeth_card *card)
 		card->qdio.out_qs[i]->bufs[j] = NULL;
 	}
 out_freeoutq:
-	while (i > 0) {
-		qeth_free_qdio_out_buf(card->qdio.out_qs[--i]);
-		qeth_clear_outq_buffers(card->qdio.out_qs[i], 1);
-	}
+	while (i > 0)
+		qeth_free_output_queue(card->qdio.out_qs[--i]);
 	kfree(card->qdio.out_qs);
 	card->qdio.out_qs = NULL;
 out_freepool:
@@ -2573,10 +2572,8 @@ static void qeth_free_qdio_buffers(struct qeth_card *card)
 	qeth_free_buffer_pool(card);
 	/* free outbound qdio_qs */
 	if (card->qdio.out_qs) {
-		for (i = 0; i < card->qdio.no_out_queues; ++i) {
-			qeth_clear_outq_buffers(card->qdio.out_qs[i], 1);
-			qeth_free_qdio_out_buf(card->qdio.out_qs[i]);
-		}
+		for (i = 0; i < card->qdio.no_out_queues; i++)
+			qeth_free_output_queue(card->qdio.out_qs[i]);
 		kfree(card->qdio.out_qs);
 		card->qdio.out_qs = NULL;
 	}