From abe84903a8efc6b83fa92161429e0e3a28bde15c Mon Sep 17 00:00:00 2001 From: Johan Hedberg Date: Wed, 12 Nov 2014 22:22:21 +0200 Subject: 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 Signed-off-by: Marcel Holtmann --- net/bluetooth/l2cap_sock.c | 9 +++++++++ net/bluetooth/smp.c | 10 ++++++++++ 2 files changed, 19 insertions(+) (limited to 'net/bluetooth') diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index ad1cf82fee02..f1a51564b8fd 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -285,6 +285,12 @@ static int l2cap_sock_listen(struct socket *sock, int backlog) 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 @@ static void l2cap_sock_init(struct sock *sk, struct sock *parent) 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; diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c index 3d38553eb526..3b63c7f09dd5 100644 --- a/net/bluetooth/smp.c +++ b/net/bluetooth/smp.c @@ -1658,6 +1658,13 @@ static inline struct l2cap_chan *smp_new_conn_cb(struct l2cap_chan *pchan) chan->omtu = pchan->omtu; chan->mode = pchan->mode; + /* Other L2CAP channels may request SMP routines in order to + * change the security level. This means that the SMP channel + * lock must be considered in its own category to avoid lockdep + * warnings. + */ + atomic_set(&chan->nesting, L2CAP_NESTING_SMP); + BT_DBG("created chan %p", chan); return chan; @@ -1715,6 +1722,9 @@ int smp_register(struct hci_dev *hdev) chan->imtu = L2CAP_DEFAULT_MTU; chan->ops = &smp_root_chan_ops; + /* Set correct nesting level for a parent/listening channel */ + atomic_set(&chan->nesting, L2CAP_NESTING_PARENT); + hdev->smp_data = chan; return 0; -- cgit v1.2.3