Bluetooth: Use proper nesting annotation for l2cap_chan lock
By default lockdep considers all L2CAP channels equal. This would mean
that we get warnings if a channel is locked when another one's lock is
tried to be acquired in the same thread. This kind of inter-channel
locking dependencies exist in the form of parent-child channels as well
as any channel wishing to elevate the security by requesting procedures
on the SMP channel.
To eliminate the chance for these lockdep warnings we introduce a
nesting level for each channel and use that when acquiring the channel
lock. For now there exists the earlier mentioned three identified
categories: SMP, "normal" channels and parent channels (i.e. those in
BT_LISTEN state). The nesting level is defined as atomic_t since we need
access to it before the lock is actually acquired.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index ad1cf82..f1a5156 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -285,6 +285,12 @@
sk->sk_max_ack_backlog = backlog;
sk->sk_ack_backlog = 0;
+ /* Listening channels need to use nested locking in order not to
+ * cause lockdep warnings when the created child channels end up
+ * being locked in the same thread as the parent channel.
+ */
+ atomic_set(&chan->nesting, L2CAP_NESTING_PARENT);
+
chan->state = BT_LISTEN;
sk->sk_state = BT_LISTEN;
@@ -1497,6 +1503,9 @@
l2cap_chan_set_defaults(chan);
}
+ /* Set default lock nesting level */
+ atomic_set(&chan->nesting, L2CAP_NESTING_NORMAL);
+
/* Default config options */
chan->flush_to = L2CAP_DEFAULT_FLUSH_TO;