Bluetooth: reorganize functions from hci_sock_sendmsg()

Since userfaultfd mechanism allows sleeping with kernel lock held,
avoiding page fault with kernel lock held where possible will make
the module more robust. This patch just brings memcpy_from_msg() calls
to out of sock lock.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

net/bluetooth/hci_sock.c

@@ -1505,10 +1505,8 @@ static int hci_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 	return err ? : copied;
 }
 
-static int hci_mgmt_cmd(struct hci_mgmt_chan *chan, struct sock *sk,
-			struct msghdr *msg, size_t msglen)
+static int hci_mgmt_cmd(struct hci_mgmt_chan *chan, struct sock *sk, void *buf, size_t msglen)
 {
-	void *buf;
 	u8 *cp;
 	struct mgmt_hdr *hdr;
 	u16 opcode, index, len;
@@ -1522,15 +1520,6 @@ static int hci_mgmt_cmd(struct hci_mgmt_chan *chan, struct sock *sk,
 	if (msglen < sizeof(*hdr))
 		return -EINVAL;
 
-	buf = kmalloc(msglen, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	if (memcpy_from_msg(buf, msg, msglen)) {
-		err = -EFAULT;
-		goto done;
-	}
-
 	hdr = buf;
 	opcode = __le16_to_cpu(hdr->opcode);
 	index = __le16_to_cpu(hdr->index);
@@ -1627,11 +1616,10 @@ static int hci_mgmt_cmd(struct hci_mgmt_chan *chan, struct sock *sk,
 	if (hdev)
 		hci_dev_put(hdev);
 
-	kfree(buf);
 	return err;
 }
 
-static int hci_logging_frame(struct sock *sk, struct msghdr *msg, int len)
+static int hci_logging_frame(struct sock *sk, void *buf, int len, unsigned int flags)
 {
 	struct hci_mon_hdr *hdr;
 	struct sk_buff *skb;
@@ -1646,14 +1634,11 @@ static int hci_logging_frame(struct sock *sk, struct msghdr *msg, int len)
 	if (len < sizeof(*hdr) + 3)
 		return -EINVAL;
 
-	skb = bt_skb_send_alloc(sk, len, msg->msg_flags & MSG_DONTWAIT, &err);
+	skb = bt_skb_send_alloc(sk, len, flags & MSG_DONTWAIT, &err);
 	if (!skb)
 		return err;
 
-	if (memcpy_from_msg(skb_put(skb, len), msg, len)) {
-		err = -EFAULT;
-		goto drop;
-	}
+	memcpy(skb_put(skb, len), buf, len);
 
 	hdr = (void *)skb->data;
 
@@ -1723,19 +1708,28 @@ static int hci_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 	struct hci_dev *hdev;
 	struct sk_buff *skb;
 	int err;
+	void *buf;
+	const unsigned int flags = msg->msg_flags;
 
 	BT_DBG("sock %p sk %p", sock, sk);
 
-	if (msg->msg_flags & MSG_OOB)
+	if (flags & MSG_OOB)
 		return -EOPNOTSUPP;
 
-	if (msg->msg_flags & ~(MSG_DONTWAIT|MSG_NOSIGNAL|MSG_ERRQUEUE|
-			       MSG_CMSG_COMPAT))
+	if (flags & ~(MSG_DONTWAIT | MSG_NOSIGNAL | MSG_ERRQUEUE | MSG_CMSG_COMPAT))
 		return -EINVAL;
 
 	if (len < 4 || len > HCI_MAX_FRAME_SIZE)
 		return -EINVAL;
 
+	buf = kmalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+	if (memcpy_from_msg(buf, msg, len)) {
+		kfree(buf);
+		return -EFAULT;
+	}
+
 	lock_sock(sk);
 
 	switch (hci_pi(sk)->channel) {
@@ -1746,13 +1740,13 @@ static int hci_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 		err = -EOPNOTSUPP;
 		goto done;
 	case HCI_CHANNEL_LOGGING:
-		err = hci_logging_frame(sk, msg, len);
+		err = hci_logging_frame(sk, buf, len, flags);
 		goto done;
 	default:
 		mutex_lock(&mgmt_chan_list_lock);
 		chan = __hci_mgmt_chan_find(hci_pi(sk)->channel);
 		if (chan)
-			err = hci_mgmt_cmd(chan, sk, msg, len);
+			err = hci_mgmt_cmd(chan, sk, buf, len);
 		else
 			err = -EINVAL;
 
@@ -1771,14 +1765,11 @@ static int hci_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 		goto done;
 	}
 
-	skb = bt_skb_send_alloc(sk, len, msg->msg_flags & MSG_DONTWAIT, &err);
+	skb = bt_skb_send_alloc(sk, len, flags & MSG_DONTWAIT, &err);
 	if (!skb)
 		goto done;
 
-	if (memcpy_from_msg(skb_put(skb, len), msg, len)) {
-		err = -EFAULT;
-		goto drop;
-	}
+	memcpy(skb_put(skb, len), buf, len);
 
 	hci_skb_pkt_type(skb) = skb->data[0];
 	skb_pull(skb, 1);
@@ -1850,6 +1841,7 @@ static int hci_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 
 done:
 	release_sock(sk);
+	kfree(buf);
 	return err;
 
 drop: