linux-kernel - [PATCH 3.16 100/294] scsi: st: fix blk_get

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Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Kai Mäkisara" <kai.makisara@...umbus.fi>,
        "Bodo Stroesser" <bstroesser@...fujitsu.com>,
        "Hannes Reinecke" <hare@...e.com>,
        "Shirish Pargaonkar" <spargaonkar@...e.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Ewan D. Milne" <emilne@...hat.com>
Subject: [PATCH 3.16 100/294] scsi: st: fix blk_get_queue usage

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Bodo Stroesser <bstroesser@...fujitsu.com>

commit 180efde0a3f43dbe533e4be203c2918793482d4e upstream.

If blk_queue_get() in st_probe fails, disk->queue must not be set to
SDp->request_queue, as that would result in put_disk() dropping a not
taken reference.

Thus, disk->queue should be set only after a successful blk_queue_get().

Fixes: 2b5bebccd282 ("st: Take additional queue ref in st_probe")
Signed-off-by: Bodo Stroesser <bstroesser@...fujitsu.com>
Acked-by: Shirish Pargaonkar <spargaonkar@...e.com>
Signed-off-by: Hannes Reinecke <hare@...e.com>
Reviewed-by: Ewan D. Milne <emilne@...hat.com>
Acked-by: Kai Mäkisara <kai.makisara@...umbus.fi>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/st.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -4115,11 +4115,11 @@ static int st_probe(struct device *dev)
 	kref_init(&tpnt->kref);
 	tpnt->disk = disk;
 	disk->private_data = &tpnt->driver;
-	disk->queue = SDp->request_queue;
 	/* SCSI tape doesn't register this gendisk via add_disk().  Manually
 	 * take queue reference that release_disk() expects. */
-	if (!blk_get_queue(disk->queue))
+	if (!blk_get_queue(SDp->request_queue))
 		goto out_put_disk;
+	disk->queue = SDp->request_queue;
 	tpnt->driver = &st_template;
 
 	tpnt->device = SDp;