can: netlink: can_validate(): validate sample point for CAN and CAN-FD

The sample point is a value in tenths of a percent. Meaningful values
are between 0 and 1000. Invalid values are rejected and an error
message is returned to user space via netlink.

Link: https://lore.kernel.org/all/20230202110854.2318594-8-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/dev/netlink.c

@@ -36,10 +36,24 @@ static const struct nla_policy can_tdc_policy[IFLA_CAN_TDC_MAX + 1] = {
 	[IFLA_CAN_TDC_TDCF] = { .type = NLA_U32 },
 };
 
+static int can_validate_bittiming(const struct can_bittiming *bt,
+				  struct netlink_ext_ack *extack)
+{
+	/* sample point is in one-tenth of a percent */
+	if (bt->sample_point >= 1000) {
+		NL_SET_ERR_MSG(extack, "sample point must be between 0 and 100%");
+
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 			struct netlink_ext_ack *extack)
 {
 	bool is_can_fd = false;
+	int err;
 
 	/* Make sure that valid CAN FD configurations always consist of
 	 * - nominal/arbitration bittiming
@@ -51,6 +65,15 @@ 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;
@@ -71,7 +94,6 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 		 */
 		if (data[IFLA_CAN_TDC]) {
 			struct nlattr *tb_tdc[IFLA_CAN_TDC_MAX + 1];
-			int err;
 
 			err = nla_parse_nested(tb_tdc, IFLA_CAN_TDC_MAX,
 					       data[IFLA_CAN_TDC],
@@ -102,6 +124,15 @@ static int can_validate(struct nlattr *tb[], struct nlattr *data[],
 			return -EOPNOTSUPP;
 	}
 
+	if (data[IFLA_CAN_DATA_BITTIMING]) {
+		struct can_bittiming bt;
+
+		memcpy(&bt, nla_data(data[IFLA_CAN_DATA_BITTIMING]), sizeof(bt));
+		err = can_validate_bittiming(&bt, extack);
+		if (err)
+			return err;
+	}
+
 	return 0;
 }