Bluetooth: L2CAP: Fix deadlock

This fixes the following deadlock introduced by 39a92a55be13
("bluetooth/l2cap: sync sock recv cb and release")

============================================
WARNING: possible recursive locking detected
6.10.0-rc3-g4029dba6b6f1 #6823 Not tainted
--------------------------------------------
kworker/u5:0/35 is trying to acquire lock:
ffff888002ec2510 (&chan->lock#2/1){+.+.}-{3:3}, at:
l2cap_sock_recv_cb+0x44/0x1e0

but task is already holding lock:
ffff888002ec2510 (&chan->lock#2/1){+.+.}-{3:3}, at:
l2cap_get_chan_by_scid+0xaf/0xd0

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&chan->lock#2/1);
  lock(&chan->lock#2/1);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by kworker/u5:0/35:
 #0: ffff888002b8a940 ((wq_completion)hci0#2){+.+.}-{0:0}, at:
process_one_work+0x750/0x930
 #1: ffff888002c67dd0 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0},
at: process_one_work+0x44e/0x930
 #2: ffff888002ec2510 (&chan->lock#2/1){+.+.}-{3:3}, at:
l2cap_get_chan_by_scid+0xaf/0xd0

To fix the original problem this introduces l2cap_chan_lock at
l2cap_conless_channel to ensure that l2cap_sock_recv_cb is called with
chan->lock held.

Fixes: 89e856e124f9 ("bluetooth/l2cap: sync sock recv cb and release")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index a8a7d2b36870..eea34e6a236f 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -280,6 +280,19 @@ int __hci_cmd_sync_status(struct hci_dev *hdev, u16 opcode, u32 plen,
 }
 EXPORT_SYMBOL(__hci_cmd_sync_status);
 
+int hci_cmd_sync_status(struct hci_dev *hdev, u16 opcode, u32 plen,
+			const void *param, u32 timeout)
+{
+	int err;
+
+	hci_req_sync_lock(hdev);
+	err = __hci_cmd_sync_status(hdev, opcode, plen, param, timeout);
+	hci_req_sync_unlock(hdev);
+
+	return err;
+}
+EXPORT_SYMBOL(hci_cmd_sync_status);
+
 static void hci_cmd_sync_work(struct work_struct *work)
 {
 	struct hci_dev *hdev = container_of(work, struct hci_dev, cmd_sync_work);