[PATCH net-next v3] net/ionic: avoid OOB TX partner lookup for hwstamp RXQ

[Anand Khoje]

The dedicated hardware timestamp RX queue is allocated with q->index
equal to lif->ionic->nrxqs_per_lif. The normal txqcqs array only
contains the regular queue pairs, so using that index to set rxq->partner
can read one entry past txqcqs[] and then write through the derived
pointer.
Only link RX/TX partners for normal queue-pair indexes. Leave the hwstamp
RX queue unpaired, and make the XDP_TX path abort cleanly if an RX queue
has no TX partner.

Fixes: 8eeed8373e1c ("ionic: Add XDP_TX support")
Signed-off-by: Anand Khoje <anand.a.khoje@xxxxxxxxxx>
Reviewed-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
Reviewed-by: Shannon Nelson <sln@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
v3:
 Use dev_err() and return -ENXIO for a missing normal TX partner.

v2:
 Correct the Fixes tag.

 drivers/net/ethernet/pensando/ionic/ionic_lif.c | 17 +++++++++++++++--
 .../net/ethernet/pensando/ionic/ionic_txrx.c    |  7 ++++++-
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_lif.c b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
index fd3ee98..abc8e35 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_lif.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
@@ -920,8 +920,21 @@ static int ionic_lif_rxq_init(struct ionic_lif *lif, struct ionic_qcq *qcq)
 	};
 	int err;
 
-	q->partner = &lif->txqcqs[q->index]->q;
-	q->partner->partner = q;
+	q->partner = NULL;
+
+	/* Only normal RX queues have matching TX queue partners. */
+	if (q->index < lif->nxqs) {
+		if (!lif->txqcqs ||
+		    q->index >= lif->ionic->ntxqs_per_lif ||
+		    !lif->txqcqs[q->index]) {
+			dev_err(dev, "missing TX queue partner for RX queue %u\n",
+				q->index);
+			return -ENXIO;
+		}
+
+		q->partner = &lif->txqcqs[q->index]->q;
+		q->partner->partner = q;
+	}
 
 	if (!lif->xdp_prog ||
 	    (lif->xdp_prog->aux && lif->xdp_prog->aux->xdp_has_frags))
diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
index 301ebee..73998d6 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
+++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
@@ -545,13 +545,18 @@ static bool ionic_run_xdp(struct ionic_rx_stats *stats,
 		break;
 
 	case XDP_TX:
+		txq = rxq->partner;
+		if (unlikely(!txq)) {
+			err = -EIO;
+			break;
+		}
+
 		xdpf = xdp_convert_buff_to_frame(&xdp_buf);
 		if (!xdpf) {
 			err = -ENOSPC;
 			break;
 		}
 
-		txq = rxq->partner;
 		nq = netdev_get_tx_queue(netdev, txq->index);
 		__netif_tx_lock(nq, smp_processor_id());
 		txq_trans_cond_update(nq);
-- 
2.52.0