netdev - [PATCH net] ionic: catch NULL pointer issue on reconfig

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Message-Id: <20221017233123.15869-1-snelson@pensando.io>
Date:   Mon, 17 Oct 2022 16:31:23 -0700
From:   Shannon Nelson <snelson@...sando.io>
To:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org
Cc:     drivers@...sando.io, Brett Creeley <brett@...sando.io>,
        Shannon Nelson <snelson@...sando.io>
Subject: [PATCH net] ionic: catch NULL pointer issue on reconfig

From: Brett Creeley <brett@...sando.io>

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: 101b40a0171f ("ionic: change queue count with no reset")
Signed-off-by: Brett Creeley <brett@...sando.io>
Signed-off-by: Shannon Nelson <snelson@...sando.io>
---
 drivers/net/ethernet/pensando/ionic/ionic_lif.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/pensando/ionic/ionic_lif.c b/drivers/net/ethernet/pensando/ionic/ionic_lif.c
index 5d58fd99be3c..19d4848df17d 100644
--- a/drivers/net/ethernet/pensando/ionic/ionic_lif.c
+++ b/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)
-- 
2.17.1