net: dsa: sja1105: reject other RX filters than HWTSTAMP_FILTER_PTP_V2_L2_EVENT

This is all that we can support timestamping, so we shouldn't accept
anything else. Also see sja1105_hwtstamp_get().

To avoid erroring out in an inconsistent state, operate on copies of
priv->hwts_rx_en and priv->hwts_tx_en, and write them back when nothing
else can fail anymore.

Fixes: a602afd ("net: dsa: sja1105: Expose PTP timestamping ioctls to userspace")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250318115716.2124395-3-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: vladimiroltean

drivers/net/dsa/sja1105/sja1105_ptp.c

@@ -61,33 +61,43 @@ enum sja1105_ptp_clk_mode {
 int sja1105_hwtstamp_set(struct dsa_switch *ds, int port, struct ifreq *ifr)
 {
 	struct sja1105_private *priv = ds->priv;
+	unsigned long hwts_tx_en, hwts_rx_en;
 	struct hwtstamp_config config;
 
 	if (copy_from_user(&config, ifr->ifr_data, sizeof(config)))
 		return -EFAULT;
 
+	hwts_tx_en = priv->hwts_tx_en;
+	hwts_rx_en = priv->hwts_rx_en;
+
 	switch (config.tx_type) {
 	case HWTSTAMP_TX_OFF:
-		priv->hwts_tx_en &= ~BIT(port);
+		hwts_tx_en &= ~BIT(port);
 		break;
 	case HWTSTAMP_TX_ON:
-		priv->hwts_tx_en |= BIT(port);
+		hwts_tx_en |= BIT(port);
 		break;
 	default:
 		return -ERANGE;
 	}
 
 	switch (config.rx_filter) {
 	case HWTSTAMP_FILTER_NONE:
-		priv->hwts_rx_en &= ~BIT(port);
+		hwts_rx_en &= ~BIT(port);
 		break;
-	default:
-		priv->hwts_rx_en |= BIT(port);
+	case HWTSTAMP_FILTER_PTP_V2_L2_EVENT:
+		hwts_rx_en |= BIT(port);
 		break;
+	default:
+		return -ERANGE;
 	}
 
 	if (copy_to_user(ifr->ifr_data, &config, sizeof(config)))
 		return -EFAULT;
+
+	priv->hwts_tx_en = hwts_tx_en;
+	priv->hwts_rx_en = hwts_rx_en;
+
 	return 0;
 }