From: Johan Hedberg <johan.hedberg@xxxxxxxxx>
Any code calling bt_accept_dequeue() to get a new child socket from a
server socket should use lock_sock_nested to avoid lockdep warnings due
to the parent and child sockets being locked at the same time. The
l2cap_sock_accept() function is already doing this correctly but a
second place calling bt_accept_dequeue() is the code path from
l2cap_sock_teardown_cb() that calls l2cap_sock_cleanup_listen().
This patch fixes the proper nested locking annotation and thereby avoids
the following style of lockdep warning.
[ +0.000224] [ INFO: possible recursive locking detected ]
[ +0.000222] 3.17.0+ #1153 Not tainted
[ +0.000130] ---------------------------------------------
[ +0.000227] l2cap-tester/562 is trying to acquire lock:
[ +0.000210] (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}, at: [<c1393f47>] bt_accept_dequeue+0x68/0x11b
[ +0.000467]
but task is already holding lock:
[ +0.000186] (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+...}, at: [<c13b949a>] lock_sock+0xa/0xc
[ +0.000421]
other info that might help us debug this:
[ +0.000199] Possible unsafe locking scenario:
[ +0.000117] CPU0
[ +0.000000] ----
[ +0.000000] lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
[ +0.000000] lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
[ +0.000000]
*** DEADLOCK ***
Signed-off-by: Johan Hedberg <johan.hedberg@xxxxxxxxx>
---
net/bluetooth/l2cap_sock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 31f106e61ca2..ad1cf82fee02 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1246,7 +1246,7 @@ static void l2cap_sock_teardown_cb(struct l2cap_chan *chan, int err)
struct sock *sk = chan->data;
struct sock *parent;
- lock_sock(sk);
+ lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
parent = bt_sk(sk)->parent;
--
2.1.0
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