bcache: fix possible memory leak in bch_cached_dev_run()

memory malloced in bch_cached_dev_run() and should be freed before
leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: 0b13efecf5 ("bcache: add return value check to bch_cached_dev_run()")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/super.c

@@ -931,6 +931,9 @@ int bch_cached_dev_run(struct cached_dev *dc)
 	if (dc->io_disable) {
 		pr_err("I/O disabled on cached dev %s",
 		       dc->backing_dev_name);
+		kfree(env[1]);
+		kfree(env[2]);
+		kfree(buf);
 		return -EIO;
 	}