[PATCH v1] Bluetooth: ISO: set BT_LISTEN before requesting a BIG sync

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

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

A BIS connection is matched to its parent socket by looking for a
socket in BT_LISTEN state with the same BIG handle:

  iso_conn_ready()
    if (test_bit(HCI_CONN_BIG_SYNC, &hcon->flags))
            parent = iso_get_sock(hdev, &hcon->src, &hcon->dst,
                                  BT_LISTEN, iso_match_big_hcon, hcon);

The socket was only moved to BT_LISTEN after iso_conn_big_sync()
returned, while the LE BIG Create Sync command has already been queued
by then. If the BIG sync is established before the state is updated,
which is easy to hit with an emulated controller as the command may
complete in a few hundred microseconds, no parent is found and the BIS
connections are never notified to the listening socket.

The user space is then left waiting for connections that never arrive,
e.g. bluetoothd never completes a MediaTransport1.Acquire of a
Broadcast Sink transport.

Move the socket to BT_LISTEN before requesting the BIG sync, so the
state is visible by the time the command is queued, and restore the
previous state if the request could not be started.

Fixes: fbdc4bc47268 ("Bluetooth: ISO: Use defer setup to separate PA sync and BIG sync")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---
 net/bluetooth/iso.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index 75bfd5938b2e..dd4e1b9a7fdb 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -1737,6 +1737,13 @@ static int iso_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 		switch (sk->sk_state) {
 		case BT_CONNECT2:
 			if (test_bit(BT_SK_PA_SYNC, &pi->flags)) {
+				/* Move to BT_LISTEN before requesting the BIG
+				 * sync: the BIS connections are matched to a
+				 * parent socket in BT_LISTEN state, and they
+				 * may be notified before the request returns.
+				 */
+				sk->sk_state = BT_LISTEN;
+
 				release_sock(sk);
 				err = iso_conn_big_sync(sk);
 				lock_sock(sk);
@@ -1745,12 +1752,12 @@ static int iso_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 				 * connection may have been torn down
 				 * meanwhile and iso_chan_del() may have
 				 * already moved the socket to BT_CLOSED.
-				 * Only move on to BT_LISTEN if the BIG sync
-				 * was actually started and nothing else has
-				 * changed the state.
+				 * Only move back if the BIG sync could not be
+				 * started and nothing else has changed the
+				 * state.
 				 */
-				if (!err && sk->sk_state == BT_CONNECT2)
-					sk->sk_state = BT_LISTEN;
+				if (err && sk->sk_state == BT_LISTEN)
+					sk->sk_state = BT_CONNECT2;
 			} else {
 				iso_conn_defer_accept(pi->conn->hcon);
 				sk->sk_state = BT_CONFIG;
@@ -1760,12 +1767,17 @@ static int iso_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 			break;
 		case BT_CONNECTED:
 			if (test_bit(BT_SK_PA_SYNC, &iso_pi(sk)->flags)) {
+				/* As above, the BIS connections may be
+				 * notified before the request returns.
+				 */
+				sk->sk_state = BT_LISTEN;
+
 				release_sock(sk);
 				err = iso_conn_big_sync(sk);
 				lock_sock(sk);
 
-				if (!err && sk->sk_state == BT_CONNECTED)
-					sk->sk_state = BT_LISTEN;
+				if (err && sk->sk_state == BT_LISTEN)
+					sk->sk_state = BT_CONNECTED;
 				early_ret = true;
 			}
 
-- 
2.55.0