[PATCH net] net: ethernet: ti: icssg: guard PA stat lookups

[Philippe Schenker <dev@pschenker.ch>]

From: Philippe Schenker <philippe.schenker@impulsing.ch>

icssg_ndo_get_stats64() unconditionally calls emac_get_stat_by_name()
with FW PA stat names regardless of whether the PA stats block is
present on the hardware.  emac_get_stat_by_name() already guards the
PA stats lookup with `if (emac->prueth->pa_stats)`; when that pointer
is NULL the lookup falls through to netdev_err() and returns -EINVAL.
Because ndo_get_stats64 is polled regularly by the networking stack
this produces thousands of log entries of the form:

  icssg-prueth icssg1-eth end0: Invalid stats FW_RX_ERROR

A secondary consequence is that the int(-EINVAL) return value is
implicitly widened to a near-ULLONG_MAX unsigned value when accumulated
into the __u64 fields of rtnl_link_stats64, silently corrupting the
rx_errors, rx_dropped and tx_dropped counters reported by `ip -s link`.

Every other PA-aware code path in the driver is already guarded with
the same `if (emac->prueth->pa_stats)` check.  Apply the same guard
here.

Fixes: 0d15a26b247d ("net: ti: icssg-prueth: Add ICSSG FW Stats")

Signed-off-by: Philippe Schenker <philippe.schenker@impulsing.ch>

Cc: danishanwar@ti.com
Cc: rogerq@kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: stable@vger.kernel.org
---

 drivers/net/ethernet/ti/icssg/icssg_common.c | 48 +++++++++++---------
 1 file changed, 27 insertions(+), 21 deletions(-)

diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
index a28a608f9bf4..2dbb8f717de0 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_common.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
@@ -1628,28 +1628,34 @@ void icssg_ndo_get_stats64(struct net_device *ndev,
 	stats->rx_over_errors = emac_get_stat_by_name(emac, "rx_over_errors");
 	stats->multicast      = emac_get_stat_by_name(emac, "rx_multicast_frames");
 
-	stats->rx_errors  = ndev->stats.rx_errors +
-			    emac_get_stat_by_name(emac, "FW_RX_ERROR") +
-			    emac_get_stat_by_name(emac, "FW_RX_EOF_SHORT_FRMERR") +
-			    emac_get_stat_by_name(emac, "FW_RX_B0_DROP_EARLY_EOF") +
-			    emac_get_stat_by_name(emac, "FW_RX_EXP_FRAG_Q_DROP") +
-			    emac_get_stat_by_name(emac, "FW_RX_FIFO_OVERRUN");
-	stats->rx_dropped = ndev->stats.rx_dropped +
-			    emac_get_stat_by_name(emac, "FW_DROPPED_PKT") +
-			    emac_get_stat_by_name(emac, "FW_INF_PORT_DISABLED") +
-			    emac_get_stat_by_name(emac, "FW_INF_SAV") +
-			    emac_get_stat_by_name(emac, "FW_INF_SA_DL") +
-			    emac_get_stat_by_name(emac, "FW_INF_PORT_BLOCKED") +
-			    emac_get_stat_by_name(emac, "FW_INF_DROP_TAGGED") +
-			    emac_get_stat_by_name(emac, "FW_INF_DROP_PRIOTAGGED") +
-			    emac_get_stat_by_name(emac, "FW_INF_DROP_NOTAG") +
-			    emac_get_stat_by_name(emac, "FW_INF_DROP_NOTMEMBER");
+	stats->rx_errors  = ndev->stats.rx_errors;
+	stats->rx_dropped = ndev->stats.rx_dropped;
 	stats->tx_errors  = ndev->stats.tx_errors;
-	stats->tx_dropped = ndev->stats.tx_dropped +
-			    emac_get_stat_by_name(emac, "FW_RTU_PKT_DROP") +
-			    emac_get_stat_by_name(emac, "FW_TX_DROPPED_PACKET") +
-			    emac_get_stat_by_name(emac, "FW_TX_TS_DROPPED_PACKET") +
-			    emac_get_stat_by_name(emac, "FW_TX_JUMBO_FRM_CUTOFF");
+	stats->tx_dropped = ndev->stats.tx_dropped;
+
+	if (emac->prueth->pa_stats) {
+		stats->rx_errors  +=
+				emac_get_stat_by_name(emac, "FW_RX_ERROR") +
+				emac_get_stat_by_name(emac, "FW_RX_EOF_SHORT_FRMERR") +
+				emac_get_stat_by_name(emac, "FW_RX_B0_DROP_EARLY_EOF") +
+				emac_get_stat_by_name(emac, "FW_RX_EXP_FRAG_Q_DROP") +
+				emac_get_stat_by_name(emac, "FW_RX_FIFO_OVERRUN");
+		stats->rx_dropped +=
+				emac_get_stat_by_name(emac, "FW_DROPPED_PKT") +
+				emac_get_stat_by_name(emac, "FW_INF_PORT_DISABLED") +
+				emac_get_stat_by_name(emac, "FW_INF_SAV") +
+				emac_get_stat_by_name(emac, "FW_INF_SA_DL") +
+				emac_get_stat_by_name(emac, "FW_INF_PORT_BLOCKED") +
+				emac_get_stat_by_name(emac, "FW_INF_DROP_TAGGED") +
+				emac_get_stat_by_name(emac, "FW_INF_DROP_PRIOTAGGED") +
+				emac_get_stat_by_name(emac, "FW_INF_DROP_NOTAG") +
+				emac_get_stat_by_name(emac, "FW_INF_DROP_NOTMEMBER");
+		stats->tx_dropped +=
+				emac_get_stat_by_name(emac, "FW_RTU_PKT_DROP") +
+				emac_get_stat_by_name(emac, "FW_TX_DROPPED_PACKET") +
+				emac_get_stat_by_name(emac, "FW_TX_TS_DROPPED_PACKET") +
+				emac_get_stat_by_name(emac, "FW_TX_JUMBO_FRM_CUTOFF");
+	}
 }
 EXPORT_SYMBOL_GPL(icssg_ndo_get_stats64);
 
-- 
2.54.0

base-commit: 8cd9520d35a6c38db6567e97dd93b1f11f185dc6
branch: fix-icssg_common-pa-stats-errors__master-7-1