4.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Julian Wiedmann <jwi@xxxxxxxxxxxxx>
[ Upstream commit a702349a4099cd5a7bab0904689d8e0bf8dcd622 ]
By updating q->used_buffers only _after_ do_QDIO() has completed, there
is a potential race against the buffer's TX completion. In the unlikely
case that the TX completion path wins, qeth_qdio_output_handler() would
decrement the counter before qeth_flush_buffers() even incremented it.
Signed-off-by: Julian Wiedmann <jwi@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/s390/net/qeth_core_main.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -3530,13 +3530,14 @@ static void qeth_flush_buffers(struct qe
qdio_flags = QDIO_FLAG_SYNC_OUTPUT;
if (atomic_read(&queue->set_pci_flags_count))
qdio_flags |= QDIO_FLAG_PCI_OUT;
+ atomic_add(count, &queue->used_buffers);
+
rc = do_QDIO(CARD_DDEV(queue->card), qdio_flags,
queue->queue_no, index, count);
if (queue->card->options.performance_stats)
queue->card->perf_stats.outbound_do_qdio_time +=
qeth_get_micros() -
queue->card->perf_stats.outbound_do_qdio_start_time;
- atomic_add(count, &queue->used_buffers);
if (rc) {
queue->card->stats.tx_errors += count;
/* ignore temporary SIGA errors without busy condition */
