This is a note to let you know that I've just added the patch titled
Bluetooth: iso: Fix recursive locking warning
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bluetooth-iso-fix-recursive-locking-warning.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e4c0e40dd359dd818d8485fbe57c8536a2473f88
Author: Iulia Tanasescu <iulia.tanasescu@xxxxxxx>
Date: Wed Dec 4 14:28:49 2024 +0200
Bluetooth: iso: Fix recursive locking warning
[ Upstream commit 9bde7c3b3ad0e1f39d6df93dd1c9caf63e19e50f ]
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@xxxxxxx>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index 83597b3c0a8d..b94d202bf374 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -1120,7 +1120,11 @@ 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, flags & O_NONBLOCK);
@@ -1151,7 +1155,7 @@ 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);
