Commit 2b5bebcc authored Mar 05, 2013 by Joe Lawrence Committed by James Bottomley Apr 06, 2013

[SCSI] st: Take additional queue ref in st_probe

This patch fixes a reference count bug in the SCSI tape driver which can be
reproduced with the following:

* Boot with slub_debug=FZPU, tape drive attached
* echo 1 > /sys/devices/... tape device pci path .../remove
* Wait for device removal
* echo 1 > /sys/kernel/slab/blkdev_queue/validate
* Slub debug complains about corrupted poison pattern

In commit 523e1d39 (block: make gendisk hold a reference to its queue)
add_disk() and disk_release() were modified to get/put an additional
reference on a disk queue to fix a reference counting discrepency
between bdev release and SCSI device removal.  The ST driver never
calls add_disk(), so this commit introduced an extra kref put when the
ST driver frees its struct gendisk.

Attempts were made to fix this bug at the block level [1] but later
abandoned due to floppy driver issues [2].

[1] https://lkml.org/lkml/2012/8/27/354
[2] https://lkml.org/lkml/2012/9/22/113



Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
Tested-by: Ewan D. Milne <emilne@redhat.com>
Acked-by: Kai Mäkisara <Kai.Makisara@kolumbus.fi>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

parent 95c9f4d4

drivers/scsi/st.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -4112,6 +4112,10 @@ static int st_probe(struct device *dev)
		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))
		goto out_put_disk;
		tpnt->driver = &st_template;

		tpnt->device = SDp;
		@@ -4185,7 +4189,7 @@ static int st_probe(struct device *dev)
		idr_preload_end();
		if (error < 0) {
		pr_warn("st: idr allocation failed: %d\n", error);
		goto out_put_disk;
		goto out_put_queue;
		}
		tpnt->index = error;
		sprintf(disk->disk_name, "st%d", tpnt->index);
		@@ -4211,6 +4215,8 @@ out_remove_devs:
		spin_lock(&st_index_lock);
		idr_remove(&st_index_idr, tpnt->index);
		spin_unlock(&st_index_lock);
		out_put_queue:
		blk_put_queue(disk->queue);
		out_put_disk:
		put_disk(disk);
		kfree(tpnt);

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