platform/chrome: cros_ec_spi: drop BUG_ON() if din isn't large enough

It is overkill to crash the kernel if the `din` buffer is going to full
or overflow.

Drop the BUG_ON() and return -EINVAL instead.

Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Link: https://lore.kernel.org/r/20220513044143.1045728-8-tzungbi@kernel.org

Author: Tzung-Bi Shih

drivers/platform/chrome/cros_ec_spi.c

@@ -160,7 +160,8 @@ static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
 	struct spi_message msg;
 	int ret;
 
-	BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);
+	if (buf - ec_dev->din + n > ec_dev->din_size)
+		return -EINVAL;
 
 	memset(&trans, 0, sizeof(trans));
 	trans.cs_change = 1;
@@ -197,7 +198,8 @@ static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
 	unsigned long deadline;
 	int todo;
 
-	BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
+	if (ec_dev->din_size < EC_MSG_PREAMBLE_COUNT)
+		return -EINVAL;
 
 	/* Receive data until we see the header byte */
 	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
@@ -304,7 +306,8 @@ static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
 	unsigned long deadline;
 	int todo;
 
-	BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
+	if (ec_dev->din_size < EC_MSG_PREAMBLE_COUNT)
+		return -EINVAL;
 
 	/* Receive data until we see the header byte */
 	deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);