linux-kernel - [PATCH 5.12 229/296] vfio-ccw: Check initialized flag in cp

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Date:   Mon, 31 May 2021 15:14:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Farman <farman@...ux.ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.12 229/296] vfio-ccw: Check initialized flag in cp_init()

From: Eric Farman <farman@...ux.ibm.com>

[ 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@...ux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
Acked-by: Matthew Rosato <mjrosato@...ux.ibm.com>
Message-Id: <20210511195631.3995081-2-farman@...ux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 b9febc581b1f..8d1b2771c1aa 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -638,6 +638,10 @@ int cp_init(struct channel_program *cp, struct device *mdev, union orb *orb)
 	static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 1);
 	int ret;
 
+	/* this is an error in the caller */
+	if (cp->initialized)
+		return -EBUSY;
+
 	/*
 	 * We only support prefetching the channel program. We assume all channel
 	 * programs executed by supported guests likewise support prefetching.
-- 
2.30.2