[PATCH] Bluetooth: L2CAP: Validate PDU length before reading SDU length in l2cap_ecred_data_rcv()

[Hyunwoo Kim <imv4bel@gmail.com>]

l2cap_ecred_data_rcv() reads the SDU length field from skb->data using
get_unaligned_le16() without first verifying that skb contains at least
L2CAP_SDULEN_SIZE (2) bytes. When skb->len is less than 2, this reads
past the valid data in the skb.

The ERTM reassembly path correctly calls pskb_may_pull() before reading
the SDU length (l2cap_reassemble_sdu, L2CAP_SAR_START case). Apply the
same validation to the Enhanced Credit Based Flow Control data path.

Fixes: aac23bf63659 ("Bluetooth: Implement LE L2CAP reassembly")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
 net/bluetooth/l2cap_core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index ad98db9632fd..99e9aa104507 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -6682,6 +6682,11 @@ static int l2cap_ecred_data_rcv(struct l2cap_chan *chan, struct sk_buff *skb)
 	if (!chan->sdu) {
 		u16 sdu_len;
 
+		if (!pskb_may_pull(skb, L2CAP_SDULEN_SIZE)) {
+			err = -EINVAL;
+			goto failed;
+		}
+
 		sdu_len = get_unaligned_le16(skb->data);
 		skb_pull(skb, L2CAP_SDULEN_SIZE);
 
-- 
2.43.0