From abdc568b0540bec6d3e0afebac496adef1189b77 Mon Sep 17 00:00:00 2001 From: Kiyoshi Ueda Date: Thu, 12 Aug 2010 04:13:54 +0100 Subject: [PATCH] dm: prevent access to md being deleted 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 Signed-off-by: Jun'ichi Nomura Cc: stable@kernel.org Signed-off-by: Alasdair G Kergon --- drivers/md/dm.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index a3f21dc0..ba6934c 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2136,6 +2136,7 @@ static struct mapped_device *dm_find_md(dev_t dev) 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; -- 2.7.4