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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jan Hoeppner <hoeppner@linux.ibm.com>,
        Stefan Haberland <sth@linux.ibm.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 104/197] s390/dasd: fix panic for failed online processing
Date:   Thu, 13 Sep 2018 15:30:53 +0200
Message-Id: <20180913131845.707504089@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Haberland <sth@linux.ibm.com>

[ Upstream commit 7c6553d4db03350dad0110c3224194c19df76a8f ]

Fix a panic that occurs for a device that got an error in
dasd_eckd_check_characteristics() during online processing.
For example the read configuration data command may have failed.

If this error occurs the device is not being set online and the earlier
invoked steps during online processing are rolled back. Therefore
dasd_eckd_uncheck_device() is called which needs a valid private
structure. But this pointer is not valid if
dasd_eckd_check_characteristics() has failed.

Check for a valid device->private pointer to prevent a panic.

Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/s390/block/dasd_eckd.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -1780,6 +1780,9 @@ static void dasd_eckd_uncheck_device(str
 	struct dasd_eckd_private *private = device->private;
 	int i;
 
+	if (!private)
+		return;
+
 	dasd_alias_disconnect_device_from_lcu(device);
 	private->ned = NULL;
 	private->sneq = NULL;