[RFC 4/4] Bluetooth: RFCOMM: Replace use of memcpy_from_msg with bt_skb_sendmmsg

[Luiz Augusto von Dentz <luiz.dentz@xxxxxxxxx>]

From: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>

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@xxxxxxxxx>
---
 net/bluetooth/rfcomm/core.c | 44 ++++++++++++++++++++++++++++------
 net/bluetooth/rfcomm/sock.c | 48 ++++++++++---------------------------
 2 files changed, 49 insertions(+), 43 deletions(-)

diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index f2bacb464ccf..361a60b4a670 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -549,22 +549,52 @@ 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;
+	struct sk_buff *frag;
+	int len;
 
 	if (d->state != BT_CONNECTED)
 		return -ENOTCONN;
 
-	BT_DBG("dlc %p mtu %d len %d", d, d->mtu, len);
+	/* Queue all fragments atomically. */
+	spin_lock_bh(&d->tx_queue.lock);
 
-	if (len > d->mtu)
-		return -EINVAL;
+	len = rfcomm_dlc_send_frag(d, skb);
+	if (len < 0)
+		goto unlock;
 
-	rfcomm_make_uih(skb, d->addr);
-	skb_queue_tail(&d->tx_queue, skb);
+	skb_walk_frags(skb, frag) {
+		int ret;
+
+		ret = rfcomm_dlc_send_frag(d, frag);
+		if (ret < 0)
+			break;
+
+		len += ret;
+	}
+
+	skb_shinfo(skb)->frag_list = NULL;
+
+unlock:
+	spin_unlock_bh(&d->tx_queue.lock);
 
-	if (!test_bit(RFCOMM_TX_THROTTLED, &d->flags))
+	if (len > 0 && !test_bit(RFCOMM_TX_THROTTLED, &d->flags))
 		rfcomm_schedule();
 	return len;
 }
diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index 2c95bb58f901..9dec2ff510be 100644
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -558,6 +558,7 @@ static int rfcomm_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 {
 	struct sock *sk = sock->sk;
 	struct rfcomm_dlc *d = rfcomm_pi(sk)->dlc;
+	size_t size;
 	struct sk_buff *skb;
 	int sent;
 
@@ -574,47 +575,22 @@ 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;
+	size = min_t(size_t, len, d->mtu);
 
-	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);
-
-		err = memcpy_from_msg(skb_put(skb, size), msg, size);
-		if (err) {
-			kfree_skb(skb);
-			if (sent == 0)
-				sent = err;
-			break;
-		}
+	sent = bt_sock_wait_ready(sk, msg->msg_flags);
 
-		skb->priority = sk->sk_priority;
+	release_sock(sk);
 
-		err = rfcomm_dlc_send(d, skb);
-		if (err < 0) {
-			kfree_skb(skb);
-			if (sent == 0)
-				sent = err;
-			break;
-		}
+	if (sent)
+		return sent;
 
-		sent += size;
-		len  -= size;
-	}
+	skb = bt_skb_sendmmsg(sk, msg, len, d->mtu, RFCOMM_SKB_RESERVE);
+	if (IS_ERR_OR_NULL(skb))
+		return PTR_ERR(skb);
 
-done:
-	release_sock(sk);
+	sent = rfcomm_dlc_send(d, skb);
+	if (sent < 0)
+		kfree_skb(skb);
 
 	return sent;
 }
-- 
2.31.1