[PATCH v4] usb: gadget: ncm: Handle decoding of multiple NTB's in unwrap call

[Krishna Kurapati]

When NCM is used with hosts like Windows PC, it is observed that there are
multiple NTB's contained in one usb request giveback. Since the driver
unwraps the obtained request data assuming only one NTB is present, we
loose the subsequent NTB's present resulting in data loss.

Fix this by checking the parsed block length with the obtained data
length in usb request and continue parsing after the last byte of current
NTB.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 9f6ce4240a2b ("usb: gadget: f_ncm.c added")
Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
---
Changes in v4: Replaced void* with __le16* typecast for tmp variable
Changes in v3: Removed explicit void* typecast for ntb_ptr variable

 drivers/usb/gadget/function/f_ncm.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c
index 424bb3b666db..faf90a217419 100644
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -1171,7 +1171,8 @@ static int ncm_unwrap_ntb(struct gether *port,
 			  struct sk_buff_head *list)
 {
 	struct f_ncm	*ncm = func_to_ncm(&port->func);
-	__le16		*tmp = (void *) skb->data;
+	unsigned char	*ntb_ptr = skb->data;
+	__le16		*tmp;
 	unsigned	index, index2;
 	int		ndp_index;
 	unsigned	dg_len, dg_len2;
@@ -1184,6 +1185,10 @@ static int ncm_unwrap_ntb(struct gether *port,
 	const struct ndp_parser_opts *opts = ncm->parser_opts;
 	unsigned	crc_len = ncm->is_crc ? sizeof(uint32_t) : 0;
 	int		dgram_counter;
+	int		to_process = skb->len;
+
+parse_ntb:
+	tmp = (__le16 *)ntb_ptr;
 
 	/* dwSignature */
 	if (get_unaligned_le32(tmp) != opts->nth_sign) {
@@ -1230,7 +1235,7 @@ static int ncm_unwrap_ntb(struct gether *port,
 		 * walk through NDP
 		 * dwSignature
 		 */
-		tmp = (void *)(skb->data + ndp_index);
+		tmp = (__le16 *)(ntb_ptr + ndp_index);
 		if (get_unaligned_le32(tmp) != ncm->ndp_sign) {
 			INFO(port->func.config->cdev, "Wrong NDP SIGN\n");
 			goto err;
@@ -1287,11 +1292,11 @@ static int ncm_unwrap_ntb(struct gether *port,
 			if (ncm->is_crc) {
 				uint32_t crc, crc2;
 
-				crc = get_unaligned_le32(skb->data +
+				crc = get_unaligned_le32(ntb_ptr +
 							 index + dg_len -
 							 crc_len);
 				crc2 = ~crc32_le(~0,
-						 skb->data + index,
+						 ntb_ptr + index,
 						 dg_len - crc_len);
 				if (crc != crc2) {
 					INFO(port->func.config->cdev,
@@ -1318,7 +1323,7 @@ static int ncm_unwrap_ntb(struct gether *port,
 							 dg_len - crc_len);
 			if (skb2 == NULL)
 				goto err;
-			skb_put_data(skb2, skb->data + index,
+			skb_put_data(skb2, ntb_ptr + index,
 				     dg_len - crc_len);
 
 			skb_queue_tail(list, skb2);
@@ -1331,10 +1336,17 @@ static int ncm_unwrap_ntb(struct gether *port,
 		} while (ndp_len > 2 * (opts->dgram_item_len * 2));
 	} while (ndp_index);
 
-	dev_consume_skb_any(skb);
-
 	VDBG(port->func.config->cdev,
 	     "Parsed NTB with %d frames\n", dgram_counter);
+
+	to_process -= block_len;
+	if (to_process != 0) {
+		ntb_ptr = (unsigned char *)(ntb_ptr + block_len);
+		goto parse_ntb;
+	}
+
+	dev_consume_skb_any(skb);
+
 	return 0;
 err:
 	skb_queue_purge(list);
-- 
2.42.0