[PATCH AUTOSEL 4.9 072/107] drbd: disconnect, if the wrong UUIDs are attached on a connected peer

[Sasha Levin]

From: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>

[ Upstream commit b17b59602b6dcf8f97a7dc7bc489a48388d7063a ]

With "on-no-data-accessible suspend-io", DRBD requires the next attach
or connect to be to the very same data generation uuid tag it lost last.

If we first lost connection to the peer,
then later lost connection to our own disk,
we would usually refuse to re-connect to the peer,
because it presents the wrong data set.

However, if the peer first connects without a disk,
and then attached its disk, we accepted that same wrong data set,
which would be "unexpected" by any user of that DRBD
and cause "undefined results" (read: very likely data corruption).

The fix is to forcefully disconnect as soon as we notice that the peer
attached to the "wrong" dataset.

Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/block/drbd/drbd_receiver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 77d0f80f62f9..83957a1e15ed 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -4199,7 +4199,7 @@ static int receive_uuids(struct drbd_connection *connection, struct packet_info
 	kfree(device->p_uuid);
 	device->p_uuid = p_uuid;
 
-	if (device->state.conn < C_CONNECTED &&
+	if ((device->state.conn < C_CONNECTED || device->state.pdsk == D_DISKLESS) &&
 	    device->state.disk < D_INCONSISTENT &&
 	    device->state.role == R_PRIMARY &&
 	    (device->ed_uuid & ~((u64)1)) != (p_uuid[UI_CURRENT] & ~((u64)1))) {
-- 
2.19.1