[PATCH 1/1] greybus: gb-beagleplay: Remove use of pad bytes

[Ayush Singh]

Make gb-beagleplay greybus spec compliant by using a wrapper around HDLC
payload to include cport information.

Fixes: ec558bbfea67 ("greybus: Add BeaglePlay Linux Driver")
Reported-by: kernel test robot <yujie.liu@xxxxxxxxx>
Closes: https://lore.kernel.org/r/202311072329.Xogj7hGW-lkp@xxxxxxxxx/
Signed-off-by: Ayush Singh <ayushdevel1325@xxxxxxxxx>
---
 drivers/greybus/gb-beagleplay.c | 44 +++++++++++++++++++++++----------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/drivers/greybus/gb-beagleplay.c b/drivers/greybus/gb-beagleplay.c
index 1e70ff7e3da4..fb40ade9364f 100644
--- a/drivers/greybus/gb-beagleplay.c
+++ b/drivers/greybus/gb-beagleplay.c
@@ -85,17 +85,35 @@ struct hdlc_payload {
 	void *buf;
 };
 
+/**
+ * struct hdlc_greybus_frame - Structure to represent greybus HDLC frame
+ *
+ * @cport: cport id
+ * @hdr: greybus operation header
+ * @payload: greybus message payload
+ */
+struct hdlc_greybus_frame {
+	__le16 cport;
+	struct gb_operation_msg_hdr hdr;
+	u8 payload[];
+} __packed;
+
 static void hdlc_rx_greybus_frame(struct gb_beagleplay *bg, u8 *buf, u16 len)
 {
-	u16 cport_id;
-	struct gb_operation_msg_hdr *hdr = (struct gb_operation_msg_hdr *)buf;
+	struct hdlc_greybus_frame *gb_frame = (struct hdlc_greybus_frame *)buf;
+	u16 cport_id = le16_to_cpu(gb_frame->cport);
 
-	memcpy(&cport_id, hdr->pad, sizeof(cport_id));
+	/* Ensure that the greybus message is valid */
+	if (le16_to_cpu(gb_frame->hdr.size) > len - sizeof(cport_id)) {
+		dev_warn_ratelimited(&bg->sd->dev, "Invalid/Incomplete greybus message");
+		return;
+	}
 
 	dev_dbg(&bg->sd->dev, "Greybus Operation %u type %X cport %u status %u received",
-		hdr->operation_id, hdr->type, le16_to_cpu(cport_id), hdr->result);
+		gb_frame->hdr.operation_id, gb_frame->hdr.type, cport_id, gb_frame->hdr.result);
 
-	greybus_data_rcvd(bg->gb_hd, le16_to_cpu(cport_id), buf, len);
+	greybus_data_rcvd(bg->gb_hd, cport_id, &buf[sizeof(cport_id)],
+			  le16_to_cpu(gb_frame->hdr.size));
 }
 
 static void hdlc_rx_dbg_frame(const struct gb_beagleplay *bg, const char *buf, u16 len)
@@ -339,7 +357,7 @@ static struct serdev_device_ops gb_beagleplay_ops = {
 static int gb_message_send(struct gb_host_device *hd, u16 cport, struct gb_message *msg, gfp_t mask)
 {
 	struct gb_beagleplay *bg = dev_get_drvdata(&hd->dev);
-	struct hdlc_payload payloads[2];
+	struct hdlc_payload payloads[3];
 	__le16 cport_id = le16_to_cpu(cport);
 
 	dev_dbg(&hd->dev, "Sending greybus message with Operation %u, Type: %X on Cport %u",
@@ -348,14 +366,14 @@ static int gb_message_send(struct gb_host_device *hd, u16 cport, struct gb_messa
 	if (le16_to_cpu(msg->header->size) > RX_HDLC_PAYLOAD)
 		return dev_err_probe(&hd->dev, -E2BIG, "Greybus message too big");
 
-	memcpy(msg->header->pad, &cport_id, sizeof(cport_id));
-
-	payloads[0].buf = msg->header;
-	payloads[0].len = sizeof(*msg->header);
-	payloads[1].buf = msg->payload;
-	payloads[1].len = msg->payload_size;
+	payloads[0].buf = &cport_id;
+	payloads[0].len = sizeof(cport_id);
+	payloads[1].buf = msg->header;
+	payloads[1].len = sizeof(*msg->header);
+	payloads[2].buf = msg->payload;
+	payloads[2].len = msg->payload_size;
 
-	hdlc_tx_frames(bg, ADDRESS_GREYBUS, 0x03, payloads, 2);
+	hdlc_tx_frames(bg, ADDRESS_GREYBUS, 0x03, payloads, 3);
 	greybus_message_sent(bg->gb_hd, msg, 0);
 
 	return 0;
-- 
2.43.0