This is a note to let you know that I've just added the patch titled
Bluetooth: Fix deadlock in l2cap_conn_del()
to the 3.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bluetooth-fix-deadlock-in-l2cap_conn_del.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 Mon Sep 17 00:00:00 2001
From: Jukka Taimisto <jtt@xxxxxxxxxxxxxxx>
Date: Thu, 12 Jun 2014 10:15:13 +0000
Subject: Bluetooth: Fix deadlock in l2cap_conn_del()
From: Jukka Taimisto <jtt@xxxxxxxxxxxxxxx>
commit 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 upstream.
A deadlock occurs when PDU containing invalid SMP opcode is received on
Security Manager Channel over LE link and conn->pending_rx_work worker
has not run yet.
When LE link is created l2cap_conn_ready() is called and before
returning it schedules conn->pending_rx_work worker to hdev->workqueue.
Incoming data to SMP fixed channel is handled by l2cap_recv_frame()
which calls smp_sig_channel() to handle the SMP PDU. If
smp_sig_channel() indicates failure l2cap_conn_del() is called to delete
the connection. When deleting the connection, l2cap_conn_del() purges
the pending_rx queue and calls flush_work() to wait for the
pending_rx_work worker to complete.
Since incoming data is handled by a worker running from the same
workqueue as the pending_rx_work is being scheduled on, we will deadlock
on waiting for pending_rx_work to complete.
This patch fixes the deadlock by calling cancel_work_sync() instead of
flush_work().
Signed-off-by: Jukka Taimisto <jtt@xxxxxxxxxxxxxxx>
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/bluetooth/l2cap_core.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1657,7 +1657,13 @@ static void l2cap_conn_del(struct hci_co
kfree_skb(conn->rx_skb);
skb_queue_purge(&conn->pending_rx);
- flush_work(&conn->pending_rx_work);
+
+ /* We can not call flush_work(&conn->pending_rx_work) here since we
+ * might block if we are running on a worker from the same workqueue
+ * pending_rx_work is waiting on.
+ */
+ if (work_pending(&conn->pending_rx_work))
+ cancel_work_sync(&conn->pending_rx_work);
l2cap_unregister_all_users(conn);
Patches currently in stable-queue which might be from jtt@xxxxxxxxxxxxxxx are
queue-3.15/bluetooth-fix-deadlock-in-l2cap_conn_del.patch
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