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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, Johannes Thumshirn <jthumshirn@suse.de>,
        Hannes Reinecke <hare@suse.com>,
        Bart Van Assche <bart.vanassche@wdc.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>
Subject: [PATCH 4.16 51/68] scsi: scsi_dh: Dont look for NULL devices handlers by name
Date:   Tue, 17 Apr 2018 17:58:04 +0200
Message-Id: <20180417155751.422046299@linuxfoundation.org>
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4.16-stable review patch.  If anyone has any objections, please let me know.

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

From: Johannes Thumshirn <jthumshirn@suse.de>

commit 2ee5671e3ae35e53bb5a53a89ac8f033e4b1721f upstream.

Currently scsi_dh_lookup() doesn't check for NULL as a device name. This
combined with nvme over dm-mpath results in the following messages
emitted by device-mapper:

 device-mapper: multipath: Could not failover device 259:67: Handler scsi_dh_(null) error 14.

Let scsi_dh_lookup() fail fast on NULL names.

[mkp: typo fix]

Cc: <stable@vger.kernel.org> # v4.16
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/scsi_dh.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/scsi/scsi_dh.c
+++ b/drivers/scsi/scsi_dh.c
@@ -112,6 +112,9 @@ static struct scsi_device_handler *scsi_
 {
 	struct scsi_device_handler *dh;
 
+	if (!name || strlen(name) == 0)
+		return NULL;
+
 	dh = __scsi_dh_lookup(name);
 	if (!dh) {
 		request_module("scsi_dh_%s", name);