Bluetooth: iso: Fix recursive locking warning

JIRA: https://issues.redhat.com/browse/RHEL-74483

commit 9bde7c3
Author: Iulia Tanasescu <iulia.tanasescu@nxp.com>
Date:   Wed Dec 4 14:28:49 2024 +0200

    Bluetooth: iso: Fix recursive locking warning

    This updates iso_sock_accept to use nested locking for the parent
    socket, to avoid lockdep warnings caused because the parent and
    child sockets are locked by the same thread:

    [   41.585683] ============================================
    [   41.585688] WARNING: possible recursive locking detected
    [   41.585694] 6.12.0-rc6+ #22 Not tainted
    [   41.585701] --------------------------------------------
    [   41.585705] iso-tester/3139 is trying to acquire lock:
    [   41.585711] ffff988b29530a58 (sk_lock-AF_BLUETOOTH)
                   at: bt_accept_dequeue+0xe3/0x280 [bluetooth]
    [   41.585905]
                   but task is already holding lock:
    [   41.585909] ffff988b29533a58 (sk_lock-AF_BLUETOOTH)
                   at: iso_sock_accept+0x61/0x2d0 [bluetooth]
    [   41.586064]
                   other info that might help us debug this:
    [   41.586069]  Possible unsafe locking scenario:

    [   41.586072]        CPU0
    [   41.586076]        ----
    [   41.586079]   lock(sk_lock-AF_BLUETOOTH);
    [   41.586086]   lock(sk_lock-AF_BLUETOOTH);
    [   41.586093]
                    *** DEADLOCK ***

    [   41.586097]  May be due to missing lock nesting notation

    [   41.586101] 1 lock held by iso-tester/3139:
    [   41.586107]  #0: ffff988b29533a58 (sk_lock-AF_BLUETOOTH)
                    at: iso_sock_accept+0x61/0x2d0 [bluetooth]

    Fixes: ccf74f2 ("Bluetooth: Add BTPROTO_ISO socket type")
    Signed-off-by: Iulia Tanasescu <iulia.tanasescu@nxp.com>
    Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Signed-off-by: Bastien Nocera <bnocera@redhat.com>

Author: Bastien Nocera

net/bluetooth/iso.c

@@ -1235,7 +1235,11 @@ static int iso_sock_accept(struct socket *sock, struct socket *newsock,
 	long timeo;
 	int err = 0;
 
-	lock_sock(sk);
+	/* Use explicit nested locking to avoid lockdep warnings generated
+	 * because the parent socket and the child socket are locked on the
+	 * same thread.
+	 */
+	lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
 
 	timeo = sock_rcvtimeo(sk, arg->flags & O_NONBLOCK);
 
@@ -1266,7 +1270,7 @@ static int iso_sock_accept(struct socket *sock, struct socket *newsock,
 		release_sock(sk);
 
 		timeo = wait_woken(&wait, TASK_INTERRUPTIBLE, timeo);
-		lock_sock(sk);
+		lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
 	}
 	remove_wait_queue(sk_sleep(sk), &wait);