nbd: add missing locking to the nbd_dev_add error path

idr_remove needs external synchronization.

Fixes: 6e4df4c64881 ("nbd: reduce the nbd_index_mutex scope")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
[hch: split from a larger patch]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210825163108.50713-2-hch@lst.de
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 379032a..0c1389d 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1770,7 +1770,9 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
        return nbd;
 
 out_free_idr:
+       mutex_lock(&nbd_index_mutex);
        idr_remove(&nbd_index_idr, index);
+       mutex_unlock(&nbd_index_mutex);
 out_free_tags:
        blk_mq_free_tag_set(&nbd->tag_set);
 out_free_nbd: