diff options
author | Johan Hedberg <johan.hedberg@intel.com> | 2014-11-12 22:22:21 +0200 |
---|---|---|
committer | Marcel Holtmann <marcel@holtmann.org> | 2014-11-13 07:49:09 +0100 |
commit | abe84903a8efc6b83fa92161429e0e3a28bde15c (patch) | |
tree | 3b1b90b1c170c41bbd6fcdae92e8726024c37ade | |
parent | 24ccb9f4f7a3a5a867bbc880019cdb4b41176b63 (diff) | |
download | linux-abe84903a8efc6b83fa92161429e0e3a28bde15c.tar.bz2 |
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>
-rw-r--r-- | include/net/bluetooth/l2cap.h | 15 | ||||
-rw-r--r-- | net/bluetooth/l2cap_sock.c | 9 | ||||
-rw-r--r-- | net/bluetooth/smp.c | 10 |
3 files changed, 33 insertions, 1 deletions
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index ead99f032f7a..061e648052c8 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -28,6 +28,7 @@ #define __L2CAP_H #include <asm/unaligned.h> +#include <linux/atomic.h> /* L2CAP defaults */ #define L2CAP_DEFAULT_MTU 672 @@ -481,6 +482,7 @@ struct l2cap_chan { struct hci_conn *hs_hcon; struct hci_chan *hs_hchan; struct kref kref; + atomic_t nesting; __u8 state; @@ -713,6 +715,17 @@ enum { FLAG_HOLD_HCI_CONN, }; +/* Lock nesting levels for L2CAP channels. We need these because lockdep + * otherwise considers all channels equal and will e.g. complain about a + * connection oriented channel triggering SMP procedures or a listening + * channel creating and locking a child channel. + */ +enum { + L2CAP_NESTING_SMP, + L2CAP_NESTING_NORMAL, + L2CAP_NESTING_PARENT, +}; + enum { L2CAP_TX_STATE_XMIT, L2CAP_TX_STATE_WAIT_F, @@ -778,7 +791,7 @@ void l2cap_chan_put(struct l2cap_chan *c); static inline void l2cap_chan_lock(struct l2cap_chan *chan) { - mutex_lock(&chan->lock); + mutex_lock_nested(&chan->lock, atomic_read(&chan->nesting)); } static inline void l2cap_chan_unlock(struct l2cap_chan *chan) 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; |