Messages in this thread Patch in this message | | | Date | Tue, 24 Aug 2010 15:44:55 -0700 | From | Greg KH <> | Subject | [050/114] dm: prevent access to md being deleted |
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2.6.35-stable review patch. If anyone has any objections, please let us know.
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From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
commit abdc568b0540bec6d3e0afebac496adef1189b77 upstream.
This patch prevents access to mapped_device which is being deleted.
Currently, even after a mapped_device has been removed from the hash, it could be accessed through idr_find() using minor number. That could cause a race and NULL pointer reference below: CPU0 CPU1 ------------------------------------------------------------------ dev_remove(param) down_write(_hash_lock) dm_lock_for_deletion(md) spin_lock(_minor_lock) set_bit(DMF_DELETING) spin_unlock(_minor_lock) __hash_remove(hc) up_write(_hash_lock) dev_status(param) md = find_device(param) down_read(_hash_lock) __find_device_hash_cell(param) dm_get_md(param->dev) md = dm_find_md(dev) spin_lock(_minor_lock) md = idr_find(MINOR(dev)) spin_unlock(_minor_lock) dm_put(md) free_dev(md) dm_get(md) up_read(_hash_lock) __dev_status(md, param) dm_put(md)
This patch fixes such problems.
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/md/dm.c | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2141,6 +2141,7 @@ static struct mapped_device *dm_find_md( md = idr_find(&_minor_idr, minor); if (md && (md == MINOR_ALLOCED || (MINOR(disk_devt(dm_disk(md))) != minor) || + dm_deleting_md(md) || test_bit(DMF_FREEING, &md->flags))) { md = NULL; goto out;
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