Bluetooth: Check packet FCS earlier

This way, if FCS is enabled and the packet is corrupted, we just drop it
without read it len, which could be corrupted.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 11 insertions, 11 deletions

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 6094870d5d2a..8c9f577dd46d 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -4166,25 +4166,25 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
                 skb_pull(skb, 2);
                 len = skb->len;
 
+                /*
+                 * We can just drop the corrupted I-frame here.
+                 * Receiver will miss it and start proper recovery
+                 * procedures and ask retransmission.
+                 */
+                if (l2cap_check_fcs(pi, skb))
+                        goto drop;
+
                 if (__is_sar_start(control) && __is_iframe(control))
                         len -= 2;
 
                 if (pi->fcs == L2CAP_FCS_CRC16)
                         len -= 2;
 
-                /*
-                 * We can just drop the corrupted I-frame here.
-                 * Receiver will miss it and start proper recovery
-                 * procedures and ask retransmission.
-                 */
                 if (len > pi->mps) {
                         l2cap_send_disconn_req(pi->conn, sk);
                         goto drop;
                 }
 
-                if (l2cap_check_fcs(pi, skb))
-                        goto drop;
-
                 req_seq = __get_reqseq(control);
                 req_seq_offset = (req_seq - pi->expected_ack_seq) % 64;
                 if (req_seq_offset < 0)
@@ -4224,6 +4224,9 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
                 skb_pull(skb, 2);
                 len = skb->len;
 
+                if (l2cap_check_fcs(pi, skb))
+                        goto drop;
+
                 if (__is_sar_start(control))
                         len -= 2;
 
@@ -4233,9 +4236,6 @@ static inline int l2cap_data_channel(struct l2cap_conn *conn, u16 cid, struct sk
                 if (len > pi->mps || len < 0 || __is_sframe(control))
                         goto drop;
 
-                if (l2cap_check_fcs(pi, skb))
-                        goto drop;
-
                 tx_seq = __get_txseq(control);
 
                 if (pi->expected_tx_seq == tx_seq)