[PATCH 5.4 138/177] vfio-ccw: Check initialized flag in cp_init()

[Greg Kroah-Hartman]

From: Eric Farman <farman@xxxxxxxxxxxxx>

[ Upstream commit c6c82e0cd8125d30f2f1b29205c7e1a2f1a6785b ]

We have a really nice flag in the channel_program struct that
indicates if it had been initialized by cp_init(), and use it
as a guard in the other cp accessor routines, but not for a
duplicate call into cp_init(). The possibility of this occurring
is low, because that flow is protected by the private->io_mutex
and FSM CP_PROCESSING state. But then why bother checking it
in (for example) cp_prefetch() then?

Let's just be consistent and check for that in cp_init() too.

Fixes: 71189f263f8a3 ("vfio-ccw: make it safe to access channel programs")
Signed-off-by: Eric Farman <farman@xxxxxxxxxxxxx>
Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
Acked-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
Message-Id: <20210511195631.3995081-2-farman@xxxxxxxxxxxxx>
Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/s390/cio/vfio_ccw_cp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 3645d1720c4b..9628e0f3add3 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -636,6 +636,10 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 {
 	int ret;
 
+	/* this is an error in the caller */
+	if (cp->initialized)
+		return -EBUSY;
+
 	/*
 	 * XXX:
 	 * Only support prefetch enable mode now.
-- 
2.30.2