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author | Johan Hedberg <johan.hedberg@intel.com> | 2015-10-21 15:21:31 +0300 |
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committer | Marcel Holtmann <marcel@holtmann.org> | 2015-10-21 14:25:34 +0200 |
commit | 8ce783dc5ea3af3a213ac9b4d9d2ccfeeb9c9058 (patch) | |
tree | e09ec934362e059ce20e607b367ce3c8c44e5de9 /net/bluetooth/hci_conn.c | |
parent | 213445b2b40e87e819c7d949ae7d97c30dcd0853 (diff) | |
download | op-kernel-dev-8ce783dc5ea3af3a213ac9b4d9d2ccfeeb9c9058.zip op-kernel-dev-8ce783dc5ea3af3a213ac9b4d9d2ccfeeb9c9058.tar.gz |
Bluetooth: Fix missing hdev locking for LE scan cleanup
The hci_conn objects don't have a dedicated lock themselves but rely
on the caller to hold the hci_dev lock for most types of access. The
hci_conn_timeout() function has so far sent certain HCI commands based
on the hci_conn state which has been possible without holding the
hci_dev lock.
The recent changes to do LE scanning before connect attempts added
even more operations to hci_conn and hci_dev from hci_conn_timeout,
thereby exposing potential race conditions with the hci_dev and
hci_conn states.
As an example of such a race, here there's a timeout but an
l2cap_sock_connect() call manages to race with the cleanup routine:
[Oct21 08:14] l2cap_chan_timeout: chan ee4b12c0 state BT_CONNECT
[ +0.000004] l2cap_chan_close: chan ee4b12c0 state BT_CONNECT
[ +0.000002] l2cap_chan_del: chan ee4b12c0, conn f3141580, err 111, state BT_CONNECT
[ +0.000002] l2cap_sock_teardown_cb: chan ee4b12c0 state BT_CONNECT
[ +0.000005] l2cap_chan_put: chan ee4b12c0 orig refcnt 4
[ +0.000010] hci_conn_drop: hcon f53d56e0 orig refcnt 1
[ +0.000013] l2cap_chan_put: chan ee4b12c0 orig refcnt 3
[ +0.000063] hci_conn_timeout: hcon f53d56e0 state BT_CONNECT
[ +0.000049] hci_conn_params_del: addr ee:0d:30:09:53:1f (type 1)
[ +0.000002] hci_chan_list_flush: hcon f53d56e0
[ +0.000001] hci_chan_del: hci0 hcon f53d56e0 chan f4e7ccc0
[ +0.004528] l2cap_sock_create: sock e708fc00
[ +0.000023] l2cap_chan_create: chan ee4b1770
[ +0.000001] l2cap_chan_hold: chan ee4b1770 orig refcnt 1
[ +0.000002] l2cap_sock_init: sk ee4b3390
[ +0.000029] l2cap_sock_bind: sk ee4b3390
[ +0.000010] l2cap_sock_setsockopt: sk ee4b3390
[ +0.000037] l2cap_sock_connect: sk ee4b3390
[ +0.000002] l2cap_chan_connect: 00:02:72:d9:e5:8b -> ee:0d:30:09:53:1f (type 2) psm 0x00
[ +0.000002] hci_get_route: 00:02:72:d9:e5:8b -> ee:0d:30:09:53:1f
[ +0.000001] hci_dev_hold: hci0 orig refcnt 8
[ +0.000003] hci_conn_hold: hcon f53d56e0 orig refcnt 0
Above the l2cap_chan_connect() shouldn't have been able to reach the
hci_conn f53d56e0 anymore but since hci_conn_timeout didn't do proper
locking that's not the case. The end result is a reference to hci_conn
that's not in the conn_hash list, resulting in list corruption when
trying to remove it later:
[Oct21 08:15] l2cap_chan_timeout: chan ee4b1770 state BT_CONNECT
[ +0.000004] l2cap_chan_close: chan ee4b1770 state BT_CONNECT
[ +0.000003] l2cap_chan_del: chan ee4b1770, conn f3141580, err 111, state BT_CONNECT
[ +0.000001] l2cap_sock_teardown_cb: chan ee4b1770 state BT_CONNECT
[ +0.000005] l2cap_chan_put: chan ee4b1770 orig refcnt 4
[ +0.000002] hci_conn_drop: hcon f53d56e0 orig refcnt 1
[ +0.000015] l2cap_chan_put: chan ee4b1770 orig refcnt 3
[ +0.000038] hci_conn_timeout: hcon f53d56e0 state BT_CONNECT
[ +0.000003] hci_chan_list_flush: hcon f53d56e0
[ +0.000002] hci_conn_hash_del: hci0 hcon f53d56e0
[ +0.000001] ------------[ cut here ]------------
[ +0.000461] WARNING: CPU: 0 PID: 1782 at lib/list_debug.c:56 __list_del_entry+0x3f/0x71()
[ +0.000839] list_del corruption, f53d56e0->prev is LIST_POISON2 (00000200)
The necessary fix is unfortunately more complicated than just adding
hci_dev_lock/unlock calls to the hci_conn_timeout() call path.
Particularly, the hci_conn_del() API, which expects the hci_dev lock to
be held, performs a cancel_delayed_work_sync(&hcon->disc_work) which
would lead to a deadlock if the hci_conn_timeout() call path tries to
acquire the same lock.
This patch solves the problem by deferring the cleanup work to a
separate work callback. To protect against the hci_dev or hci_conn
going away meanwhile temporary references are taken with the help of
hci_dev_hold() and hci_conn_get().
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org # 4.3
Diffstat (limited to 'net/bluetooth/hci_conn.c')
-rw-r--r-- | net/bluetooth/hci_conn.c | 52 |
1 files changed, 43 insertions, 9 deletions
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c index 2dda439..ec4836f 100644 --- a/net/bluetooth/hci_conn.c +++ b/net/bluetooth/hci_conn.c @@ -137,18 +137,51 @@ static void hci_conn_cleanup(struct hci_conn *conn) hci_conn_put(conn); } -/* This function requires the caller holds hdev->lock */ -static void hci_connect_le_scan_remove(struct hci_conn *conn) +static void le_scan_cleanup(struct work_struct *work) { - hci_connect_le_scan_cleanup(conn); + struct hci_conn *conn = container_of(work, struct hci_conn, + le_scan_cleanup); + struct hci_dev *hdev = conn->hdev; + struct hci_conn *c = NULL; - /* We can't call hci_conn_del here since that would deadlock - * with trying to call cancel_delayed_work_sync(&conn->disc_work). - * Instead, call just hci_conn_cleanup() which contains the bare - * minimum cleanup operations needed for a connection in this - * state. + BT_DBG("%s hcon %p", hdev->name, conn); + + hci_dev_lock(hdev); + + /* Check that the hci_conn is still around */ + rcu_read_lock(); + list_for_each_entry_rcu(c, &hdev->conn_hash.list, list) { + if (c == conn) + break; + } + rcu_read_unlock(); + + if (c == conn) { + hci_connect_le_scan_cleanup(conn); + hci_conn_cleanup(conn); + } + + hci_dev_unlock(hdev); + hci_dev_put(hdev); + hci_conn_put(conn); +} + +static void hci_connect_le_scan_remove(struct hci_conn *conn) +{ + BT_DBG("%s hcon %p", conn->hdev->name, conn); + + /* We can't call hci_conn_del/hci_conn_cleanup here since that + * could deadlock with another hci_conn_del() call that's holding + * hci_dev_lock and doing cancel_delayed_work_sync(&conn->disc_work). + * Instead, grab temporary extra references to the hci_dev and + * hci_conn and perform the necessary cleanup in a separate work + * callback. */ - hci_conn_cleanup(conn); + + hci_dev_hold(conn->hdev); + hci_conn_get(conn); + + schedule_work(&conn->le_scan_cleanup); } static void hci_acl_create_connection(struct hci_conn *conn) @@ -580,6 +613,7 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst, INIT_DELAYED_WORK(&conn->auto_accept_work, hci_conn_auto_accept); INIT_DELAYED_WORK(&conn->idle_work, hci_conn_idle); INIT_DELAYED_WORK(&conn->le_conn_timeout, le_conn_timeout); + INIT_WORK(&conn->le_scan_cleanup, le_scan_cleanup); atomic_set(&conn->refcnt, 0); |