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

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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 <redacted>
Reviewed-by: Si-Wei Liu <redacted>
Reviewed-by: Shannon Nelson <redacted>
Cc: stable@vger.kernel.org
---
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);