ovl: fix uninitialized pointer read in ovl_lookup_real_one()

mainline inclusion
from mainline-v5.14-rc6
commit 580c6104
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I51PNB


CVE: NA

--------------------------------

One error path can result in release_dentry_name_snapshot() being called
before "name" was initialized by take_dentry_name_snapshot().

Fix by moving the release_dentry_name_snapshot() to immediately after the
only use.

Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

conflicts:
	fs/overlayfs/export.c
Signed-off-by: Zheng Liang <zhengliang6@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>