Bluetooth: RFCOMM: Replace use of memcpy_from_msg with bt_skb_sendmmsg

This makes use of bt_skb_sendmmsg instead using memcpy_from_msg which
is not considered safe to be used when lock_sock is held.

Also make rfcomm_dlc_send handle skb with fragments and queue them all
atomically.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/rfcomm/core.c

@@ -549,22 +549,58 @@ struct rfcomm_dlc *rfcomm_dlc_exists(bdaddr_t *src, bdaddr_t *dst, u8 channel)
 	return dlc;
 }
 
+static int rfcomm_dlc_send_frag(struct rfcomm_dlc *d, struct sk_buff *frag)
+{
+	int len = frag->len;
+
+	BT_DBG("dlc %p mtu %d len %d", d, d->mtu, len);
+
+	if (len > d->mtu)
+		return -EINVAL;
+
+	rfcomm_make_uih(frag, d->addr);
+	__skb_queue_tail(&d->tx_queue, frag);
+
+	return len;
+}
+
 int rfcomm_dlc_send(struct rfcomm_dlc *d, struct sk_buff *skb)
 {
-	int len = skb->len;
+	unsigned long flags;
+	struct sk_buff *frag, *next;
+	int len;
 
 	if (d->state != BT_CONNECTED)
 		return -ENOTCONN;
 
-	BT_DBG("dlc %p mtu %d len %d", d, d->mtu, len);
+	frag = skb_shinfo(skb)->frag_list;
+	skb_shinfo(skb)->frag_list = NULL;
 
-	if (len > d->mtu)
-		return -EINVAL;
+	/* Queue all fragments atomically. */
+	spin_lock_irqsave(&d->tx_queue.lock, flags);
 
-	rfcomm_make_uih(skb, d->addr);
-	skb_queue_tail(&d->tx_queue, skb);
+	len = rfcomm_dlc_send_frag(d, skb);
+	if (len < 0 || !frag)
+		goto unlock;
+
+	for (; frag; frag = next) {
+		int ret;
+
+		next = frag->next;
+
+		ret = rfcomm_dlc_send_frag(d, frag);
+		if (ret < 0) {
+			kfree_skb(frag);
+			goto unlock;
+		}
+
+		len += ret;
+	}
+
+unlock:
+	spin_unlock_irqrestore(&d->tx_queue.lock, flags);
 
-	if (!test_bit(RFCOMM_TX_THROTTLED, &d->flags))
+	if (len > 0 && !test_bit(RFCOMM_TX_THROTTLED, &d->flags))
 		rfcomm_schedule();
 	return len;
 }

net/bluetooth/rfcomm/sock.c

@@ -575,46 +575,20 @@ static int rfcomm_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 	lock_sock(sk);
 
 	sent = bt_sock_wait_ready(sk, msg->msg_flags);
-	if (sent)
-		goto done;
 
-	while (len) {
-		size_t size = min_t(size_t, len, d->mtu);
-		int err;
-
-		skb = sock_alloc_send_skb(sk, size + RFCOMM_SKB_RESERVE,
-				msg->msg_flags & MSG_DONTWAIT, &err);
-		if (!skb) {
-			if (sent == 0)
-				sent = err;
-			break;
-		}
-		skb_reserve(skb, RFCOMM_SKB_HEAD_RESERVE);
+	release_sock(sk);
 
-		err = memcpy_from_msg(skb_put(skb, size), msg, size);
-		if (err) {
-			kfree_skb(skb);
-			if (sent == 0)
-				sent = err;
-			break;
-		}
+	if (sent)
+		return sent;
 
-		skb->priority = sk->sk_priority;
+	skb = bt_skb_sendmmsg(sk, msg, len, d->mtu, RFCOMM_SKB_HEAD_RESERVE,
+			      RFCOMM_SKB_TAIL_RESERVE);
+	if (IS_ERR_OR_NULL(skb))
+		return PTR_ERR(skb);
 
-		err = rfcomm_dlc_send(d, skb);
-		if (err < 0) {
+	sent = rfcomm_dlc_send(d, skb);
+	if (sent < 0)
 		kfree_skb(skb);
-			if (sent == 0)
-				sent = err;
-			break;
-		}
-
-		sent += size;
-		len  -= size;
-	}
-
-done:
-	release_sock(sk);
 
 	return sent;
 }