Bluetooth: Prevents buffer overflow on l2cap_ertm_reassembly_sdu()

The checks should be done before the the memcpy to avoid buffer
overflow.

Reported-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index fe663e9c6684..9ef01c32b3a2 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -3470,12 +3470,12 @@ static int l2cap_ertm_reassembly_sdu(struct sock *sk, struct sk_buff *skb, u16 c
                 if (!pi->sdu)
                         goto disconnect;
 
-                memcpy(skb_put(pi->sdu, skb->len), skb->data, skb->len);
-
                 pi->partial_sdu_len += skb->len;
                 if (pi->partial_sdu_len > pi->sdu_len)
                         goto drop;
 
+                memcpy(skb_put(pi->sdu, skb->len), skb->data, skb->len);
+
                 break;
 
         case L2CAP_SDU_END:
@@ -3486,8 +3486,6 @@ static int l2cap_ertm_reassembly_sdu(struct sock *sk, struct sk_buff *skb, u16 c
                         goto disconnect;
 
                 if (!(pi->conn_state & L2CAP_CONN_SAR_RETRY)) {
-                        memcpy(skb_put(pi->sdu, skb->len), skb->data, skb->len);
-
                         pi->partial_sdu_len += skb->len;
 
                         if (pi->partial_sdu_len > pi->imtu)
@@ -3495,6 +3493,8 @@ static int l2cap_ertm_reassembly_sdu(struct sock *sk, struct sk_buff *skb, u16 c
 
                         if (pi->partial_sdu_len != pi->sdu_len)
                                 goto drop;
+
+                        memcpy(skb_put(pi->sdu, skb->len), skb->data, skb->len);
                 }
 
                 _skb = skb_clone(pi->sdu, GFP_ATOMIC);