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[patch 07/25] Close race in md_probe

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From: Greg KH <gregkh@...>
To: <linux-kernel@...>, <stable@...>, Neil Brown <neilb@...>
Cc: Justin Forbes <jmforbes@...>, Zwane Mwaikambo <zwane@...>, Theodore Ts'o <tytso@...>, Randy Dunlap <rdunlap@...>, Dave Jones <davej@...>, Chuck Wolber <chuckw@...>, Chris Wedgwood <reviews@...>, Michael Krufky <mkrufky@...>, Chuck Ebbert <cebbert@...>, Domenico Andreoli <cavokz@...>, Willy Tarreau <w@...>, Rodrigo Rubira Branco <rbranco@...>, Jake Edge <jake@...>, Eugene Teo <eteo@...>, <torvalds@...>, <akpm@...>, <alan@...>, Oliver Pinter <oliver.pntr@...>
Subject: [patch 07/25] Close race in md_probe
Date: Monday, August 4, 2008 - 5:29 pm

2.6.26-stable review patch.  If anyone has any objections, please let us
know.

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

From: Neil Brown <neilb@suse.de>

[ Upstream commit f48ed538386cb41559282d989354e8f5d442d71c ]

There is a possible race in md_probe.  If two threads call md_probe
for the same device, then one could exit (having checked that
->gendisk exists) before the other has called kobject_init_and_add,
thus returning an incomplete kobj which will cause problems when
we try to add children to it.

So extend the range of protection of disks_mutex slightly to
avoid this possibility.

Signed-off-by: Neil Brown <neilb@suse.de>
CC: Oliver Pinter <oliver.pntr@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/md/md.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3326,9 +3326,9 @@ static struct kobject *md_probe(dev_t de
 	disk->queue = mddev->queue;
 	add_disk(disk);
 	mddev->gendisk = disk;
-	mutex_unlock(&disks_mutex);
 	error = kobject_init_and_add(&mddev->kobj, &md_ktype, &disk->dev.kobj,
 				     "%s", "md");
+	mutex_unlock(&disks_mutex);
 	if (error)
 		printk(KERN_WARNING "md: cannot register %s/md - name in use\n",
 		       disk->disk_name);

-- 
--
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