Commit bfc5ecdf authored Nov 08, 2006 by Alasdair G Kergon Committed by Linus Torvalds Nov 08, 2006

[PATCH] dm: fix find_device race



There is a race between dev_create() and find_device().

If the mdptr has not yet been stored against a device, find_device() needs to
behave as though no device was found.  It already returns NULL, but there is a
dm_put() missing: it must drop the reference dm_get_md() took.

The bug was introduced by dm-fix-mapped-device-ref-counting.patch.

It manifests itself if another dm ioctl attempts to reference a newly-created
device while the device creation ioctl is still running.  The consequence is
that the device cannot be removed until the machine is rebooted.  Certain udev
configurations can lead to this happening.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: <dm-devel@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent c06cb8b1

drivers/md/dm-ioctl.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -606,9 +606,14 @@ static struct hash_cell __find_device_hash_cell(struct dm_ioctl param)
		return __get_name_cell(param->name);

		md = dm_get_md(huge_decode_dev(param->dev));
		if (md)
		if (!md)
		goto out;

		mdptr = dm_get_mdptr(md);
		if (!mdptr)
		dm_put(md);

		out:
		return mdptr;
		}

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