can: netlink: avoid call to do_set_data_bittiming callback with stale can_priv::ctrlmode

This patch moves the evaluation of data[IFLA_CAN_CTRLMODE] in function
can_changelink in front of the evaluation of data[IFLA_CAN_BITTIMING].

This avoids a call to do_set_data_bittiming providing a stale
can_priv::ctrlmode with a CAN_CTRLMODE_FD flag not matching the
requested state when switching between a CAN Classic and CAN-FD bitrate.

In the same manner the evaluation of data[IFLA_CAN_CTRLMODE] in function
can_validate is also moved in front of the evaluation of
data[IFLA_CAN_BITTIMING].

This is a preparation for patches where the nominal and data bittiming
may have interdependencies on the driver side depending on the
CAN_CTRLMODE_FD flag state.
Signed-off-by: Stefan Mätje <stefan.maetje@esd.eu>
Link: https://patch.msgid.link/20240808164224.213522-1-stefan.maetje@esd.euSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev/netlink.c

@@ -65,15 +65,6 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 	if (!data)
 		return 0;
 
-	if (data[IFLA_CAN_BITTIMING]) {
-		struct can_bittiming bt;
-
-		memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt));
-		err = can_validate_bittiming(&bt, extack);
-		if (err)
-			return err;
-	}
-
 	if (data[IFLA_CAN_CTRLMODE]) {
 		struct can_ctrlmode *cm = nla_data(data[IFLA_CAN_CTRLMODE]);
 		u32 tdc_flags = cm->flags & CAN_CTRLMODE_TDC_MASK;
@@ -114,6 +105,15 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 		}
 	}
 
+	if (data[IFLA_CAN_BITTIMING]) {
+		struct can_bittiming bt;
+
+		memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt));
+		err = can_validate_bittiming(&bt, extack);
+		if (err)
+			return err;
+	}
+
 	if (is_can_fd) {
 		if (!data[IFLA_CAN_BITTIMING] || !data[IFLA_CAN_DATA_BITTIMING])
 			return -EOPNOTSUPP;
@@ -195,48 +195,6 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
 	/* We need synchronization with dev->stop() */
 	ASSERT_RTNL();
 
-	if (data[IFLA_CAN_BITTIMING]) {
-		struct can_bittiming bt;
-
-		/* Do not allow changing bittiming while running */
-		if (dev->flags & IFF_UP)
-			return -EBUSY;
-
-		/* Calculate bittiming parameters based on
-		 * bittiming_const if set, otherwise pass bitrate
-		 * directly via do_set_bitrate(). Bail out if neither
-		 * is given.
-		 */
-		if (!priv->bittiming_const && !priv->do_set_bittiming &&
-		    !priv->bitrate_const)
-			return -EOPNOTSUPP;
-
-		memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt));
-		err = can_get_bittiming(dev, &bt,
-					priv->bittiming_const,
-					priv->bitrate_const,
-					priv->bitrate_const_cnt,
-					extack);
-		if (err)
-			return err;
-
-		if (priv->bitrate_max && bt.bitrate > priv->bitrate_max) {
-			NL_SET_ERR_MSG_FMT(extack,
-					   "arbitration bitrate %u bps surpasses transceiver capabilities of %u bps",
-					   bt.bitrate, priv->bitrate_max);
-			return -EINVAL;
-		}
-
-		memcpy(&priv->bittiming, &bt, sizeof(bt));
-
-		if (priv->do_set_bittiming) {
-			/* Finally, set the bit-timing registers */
-			err = priv->do_set_bittiming(dev);
-			if (err)
-				return err;
-		}
-	}
-
 	if (data[IFLA_CAN_CTRLMODE]) {
 		struct can_ctrlmode *cm;
 		u32 ctrlstatic;
@@ -284,6 +242,48 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[],
 			priv->ctrlmode &= cm->flags | ~CAN_CTRLMODE_TDC_MASK;
 	}
 
+	if (data[IFLA_CAN_BITTIMING]) {
+		struct can_bittiming bt;
+
+		/* Do not allow changing bittiming while running */
+		if (dev->flags & IFF_UP)
+			return -EBUSY;
+
+		/* Calculate bittiming parameters based on
+		 * bittiming_const if set, otherwise pass bitrate
+		 * directly via do_set_bitrate(). Bail out if neither
+		 * is given.
+		 */
+		if (!priv->bittiming_const && !priv->do_set_bittiming &&
+		    !priv->bitrate_const)
+			return -EOPNOTSUPP;
+
+		memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt));
+		err = can_get_bittiming(dev, &bt,
+					priv->bittiming_const,
+					priv->bitrate_const,
+					priv->bitrate_const_cnt,
+					extack);
+		if (err)
+			return err;
+
+		if (priv->bitrate_max && bt.bitrate > priv->bitrate_max) {
+			NL_SET_ERR_MSG_FMT(extack,
+					   "arbitration bitrate %u bps surpasses transceiver capabilities of %u bps",
+					   bt.bitrate, priv->bitrate_max);
+			return -EINVAL;
+		}
+
+		memcpy(&priv->bittiming, &bt, sizeof(bt));
+
+		if (priv->do_set_bittiming) {
+			/* Finally, set the bit-timing registers */
+			err = priv->do_set_bittiming(dev);
+			if (err)
+				return err;
+		}
+	}
+
 	if (data[IFLA_CAN_RESTART_MS]) {
 		/* Do not allow changing restart delay while running */
 		if (dev->flags & IFF_UP)