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Groups > linux.kernel > #1719598

[PATCH 13/17] drbd: fix race between handshake and admin disconnect/down

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From: Lars Ellenberg <lars.ellenberg@linbit.com>

conn_try_disconnect() could potentialy hit the BUG_ON()
in _conn_set_state() where it iterates over _drbd_set_state()
and "asserts" via BUG_ON() that the latter was successful.

If the STATE_SENT bit was not yet visible to conn_is_valid_transition()
early in _conn_request_state(), but became visible before conn_set_state()
later in that call path, we could hit the BUG_ON() after _drbd_set_state(),
because it returned SS_IN_TRANSIENT_STATE.

To avoid that race, we better protect set_bit(SENT_STATE) with the spinlock.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 2489667..5e090a1 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1100,7 +1100,10 @@ static int conn_connect(struct drbd_connection *connection)
 	idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
 		mutex_lock(peer_device->device->state_mutex);
 
+	/* avoid a race with conn_request_state( C_DISCONNECTING ) */
+	spin_lock_irq(&connection->resource->req_lock);
 	set_bit(STATE_SENT, &connection->flags);
+	spin_unlock_irq(&connection->resource->req_lock);
 
 	idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
 		mutex_unlock(peer_device->device->state_mutex);
-- 
2.7.4

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[PATCH 00/17] DRBD updates Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 12/17] drbd: fix potential deadlock when trying to detach during handshake Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 04/17] drbd: Send P_NEG_ACK upon write error in protocol != C Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 03/17] drbd: add explicit plugging when submitting batches Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 05/17] drbd: mark symbols static where possible Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 02/17] drbd: change list_for_each_safe to while(list_first_entry_or_null) Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 01/17] drbd: introduce drbd_recv_header_maybe_unplug Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
    Re: [PATCH 01/17] drbd: introduce drbd_recv_header_maybe_unplug Jens Axboe <axboe@kernel.dk> - 2017-08-25 19:30 +0200
      Re: [PATCH 01/17] drbd: introduce drbd_recv_header_maybe_unplug Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-28 15:40 +0200
        [PATCH 01/17] drbd: introduce drbd_recv_header_maybe_unplug Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-28 16:00 +0200
  [PATCH 08/17] drbd: fix potential get_ldev/put_ldev refcount imbalance during attach Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 17/17] drbd: switch from kmalloc() to kmalloc_array() Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 07/17] drbd: new disk-option disable-write-same Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 15/17] drbd: move global variables to drbd namespace and make some static Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 16/17] drbd: abort drbd_start_resync if there is no connection Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 13/17] drbd: fix race between handshake and admin disconnect/down Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200
  [PATCH 10/17] drbd: fix rmmod cleanup, remove _all_ debugfs entries Philipp Reisner <philipp.reisner@linbit.com> - 2017-08-24 23:30 +0200

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