[PATCH 1/2] Bluetooth: ISO: fix malformed ISO_END/CONT handling

[Pauli Virtanen]

Core specification (Part C vol 4 sec 5.4.5) does not exclude empty
ISO_CONT, ISO_END packets.  We currently reject them if they are last.

If controller sends malformed sequence

    ISO_START -> rx_len = 4, ISO_CONT skb->len 4, ISO_START

that ends payload in ISO_CONT, we leak conn->rx_skb. If controller sends
too long ISO_END, we panic on skb_put. If controller sends too short
ISO_END we accept it.

Fix by marking unfinished ISO_START via conn->rx_skb != NULL.  Check
skb->len properly before skb_put.  Combine the ISO_CONT/END code paths
as they require the same initial checks. Reject too short ISO_END
packets.

Fixes: 6aba94a49bc9 ("Bluetooth: ISO: drop ISO_END frames received without prior ISO_START")
Fixes: ccf74f2390d6 ("Bluetooth: Add BTPROTO_ISO socket type")
Signed-off-by: Pauli Virtanen <pav@xxxxxx>
---
 net/bluetooth/iso.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index cd7c7c9ea4fc..2e95a153912c 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -2540,7 +2540,7 @@ int iso_recv(struct hci_dev *hdev, u16 handle, struct sk_buff *skb, u16 flags)
 	switch (pb) {
 	case ISO_START:
 	case ISO_SINGLE:
-		if (conn->rx_len) {
+		if (conn->rx_skb || conn->rx_len) {
 			BT_ERR("Unexpected start frame (len %d)", skb->len);
 			kfree_skb(conn->rx_skb);
 			conn->rx_skb = NULL;
@@ -2621,12 +2621,14 @@ int iso_recv(struct hci_dev *hdev, u16 handle, struct sk_buff *skb, u16 flags)
 		break;
 
 	case ISO_CONT:
-		BT_DBG("Cont: frag len %d (expecting %d)", skb->len,
+	case ISO_END:
+		BT_DBG("%s: frag len %d (expecting %d)",
+		       (pb == ISO_END) ? "End" : "Cont", skb->len,
 		       conn->rx_len);
 
-		if (!conn->rx_len) {
-			BT_ERR("Unexpected continuation frame (len %d)",
-			       skb->len);
+		if (!conn->rx_skb) {
+			BT_ERR("Unexpected ISO %s frame (len %d)",
+			       (pb == ISO_END) ? "End" : "Cont", skb->len);
 			goto drop;
 		}
 
@@ -2642,17 +2644,9 @@ int iso_recv(struct hci_dev *hdev, u16 handle, struct sk_buff *skb, u16 flags)
 		skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len),
 					  skb->len);
 		conn->rx_len -= skb->len;
-		break;
 
-	case ISO_END:
-		if (!conn->rx_len) {
-			BT_ERR("Unexpected end frame (len %d)", skb->len);
-			goto drop;
-		}
-
-		skb_copy_from_linear_data(skb, skb_put(conn->rx_skb, skb->len),
-					  skb->len);
-		conn->rx_len -= skb->len;
+		if (pb == ISO_CONT)
+			break;
 
 		if (!conn->rx_len) {
 			struct sk_buff *rx_skb = conn->rx_skb;
@@ -2663,6 +2657,13 @@ int iso_recv(struct hci_dev *hdev, u16 handle, struct sk_buff *skb, u16 flags)
 			 */
 			conn->rx_skb = NULL;
 			iso_recv_frame(conn, rx_skb);
+		} else {
+			BT_ERR("ISO fragment incomplete (len %d, expected %d)",
+			       skb->len, conn->rx_len);
+			kfree_skb(conn->rx_skb);
+			conn->rx_skb = NULL;
+			conn->rx_len = 0;
+			goto drop;
 		}
 		break;
 	}
-- 
2.54.0