[PATCH 01/11] Bluetooth: ISO: fix CONNECTED -> CLOSED transition on shutdown/release

[Pauli Virtanen]

Commit e824c0bbe0ec ("Bluetooth: ISO: clear iso_data always when detaching conn from hcon")
merged a version of the UAF fix that breaks releasing connected
ISO sockets. Since hci_conn::iso_data is set to NULL, iso_chan_del() won't
be called when the hci_conn disconnects, and the ISO socket does not emit
POLLHUP correctly.

Fix by retaining full hci_conn <-> iso_conn association while in
BT_DISCONNECT state, so that local disconnect via shutdown() follows
similar ISO socket code path as remote disconnect.  Use a separate flag
to track whether hci_conn_drop() is needed, instead of setting
iso_conn::hcon = NULL

In iso_sock_ready(), disallow disconnecting socket going BT_CONNECTED,
in case hcon connects while its drop is pending.

Fixes: e824c0bbe0ec ("Bluetooth: ISO: clear iso_data always when detaching conn from hcon")
Fixes: fbdc4bc47268 ("Bluetooth: ISO: Use defer setup to separate PA sync and BIG sync")
Signed-off-by: Pauli Virtanen <pav@xxxxxx>
---

Notes:
    This is rebased version of and supercedes
    
    https://lore.kernel.org/linux-bluetooth/fbd9dd573bb1ce5f38370128dd35447e2ddfed9c.1784625576.git.pav@xxxxxx/

 net/bluetooth/iso.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index babba61eb335..299a9336b5e1 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -24,8 +24,14 @@ static struct bt_sock_list iso_sk_list = {
 };
 
 /* ---- ISO connections ---- */
+enum {
+	ISO_CONN_DROPPED,
+	__ISO_CONN_NUM_FLAGS
+};
+
 struct iso_conn {
 	struct hci_conn	*hcon;
+	DECLARE_BITMAP(flags, __ISO_CONN_NUM_FLAGS);
 
 	/* @lock: spinlock protecting changes to iso_conn fields */
 	spinlock_t	lock;
@@ -107,7 +113,8 @@ static void iso_conn_free(struct kref *ref)
 
 	if (conn->hcon) {
 		conn->hcon->iso_data = NULL;
-		hci_conn_drop(conn->hcon);
+		if (!test_and_set_bit(ISO_CONN_DROPPED, conn->flags))
+			hci_conn_drop(conn->hcon);
 	}
 
 	/* Ensure no more work items will run since hci_conn has been dropped */
@@ -306,6 +313,7 @@ static int __iso_chan_add(struct iso_conn *conn, struct sock *sk,
 
 	iso_pi(sk)->conn = conn;
 	conn->sk = sk;
+	clear_bit(ISO_CONN_DROPPED, conn->flags);
 
 	if (parent)
 		bt_accept_enqueue(parent, sk, true);
@@ -835,11 +843,8 @@ static void iso_sock_disconn(struct sock *sk)
 	}
 
 	sk->sk_state = BT_DISCONN;
-	iso_conn_lock(iso_pi(sk)->conn);
-	hci_conn_drop(iso_pi(sk)->conn->hcon);
-	iso_pi(sk)->conn->hcon->iso_data = NULL;
-	iso_pi(sk)->conn->hcon = NULL;
-	iso_conn_unlock(iso_pi(sk)->conn);
+	if (!test_and_set_bit(ISO_CONN_DROPPED, iso_pi(sk)->conn->flags))
+		hci_conn_drop(iso_pi(sk)->conn->hcon);
 }
 
 static void __iso_sock_close(struct sock *sk)
@@ -2042,9 +2047,18 @@ static void iso_sock_ready(struct sock *sk)
 		return;
 
 	lock_sock(sk);
+
+	switch (sk->sk_state) {
+	case BT_DISCONN:
+	case BT_CLOSED:
+		release_sock(sk);
+		return;
+	}
+
 	iso_sock_clear_timer(sk);
 	sk->sk_state = BT_CONNECTED;
 	sk->sk_state_change(sk);
+
 	release_sock(sk);
 }
 
-- 
2.55.0