bcache: fix use-after-free problem in bcache_device_free()

In bcache_device_free(), pointer disk is referenced still in
ida_simple_remove() after blk_cleanup_disk() gets called on this
pointer. This may cause a potential panic by use-after-free on the
disk pointer.

This patch fixes the problem by calling blk_cleanup_disk() after
ida_simple_remove().

Fixes: bc70852fd104 ("bcache: convert to blk_alloc_disk/blk_cleanup_disk")
Signed-off-by: Coly Li <colyli@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: stable@vger.kernel.org # v5.14+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211103064917.67383-1-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 84a48ee..a7bb335 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -885,9 +885,9 @@ static void bcache_device_free(struct bcache_device *d)
                bcache_device_detach(d);
 
        if (disk) {
-               blk_cleanup_disk(disk);
                ida_simple_remove(&bcache_device_idx,
                                  first_minor_to_idx(disk->first_minor));
+               blk_cleanup_disk(disk);
        }
 
        bioset_exit(&d->bio_split);