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: ccf74f2390d6 ("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>

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index 8575ba749a2c5870a344db743ece0499e85ac695..ed02bda3fda376e1f2de6d495cbbd90b3fc71092 100644 (file)
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -1225,7 +1225,11 @@ 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);
 
@@ -1256,7 +1260,7 @@ 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);