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[PATCH] dm: fix find_device race

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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>
This commit is contained in:
Alasdair G Kergon 2006-11-08 17:44:42 -08:00 committed by Linus Torvalds
parent c06cb8b1c4
commit bfc5ecdf48
1 changed files with 7 additions and 2 deletions
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9
drivers/md/dm-ioctl.c
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@ -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)
mdptr = dm_get_mdptr(md);
if (!md)
goto out;
mdptr = dm_get_mdptr(md);
if (!mdptr)
dm_put(md);
out:
return mdptr;
}