Use new cifs_smb_ses_inc_refcount() helper to get an active reference
of @ses and @ses->dfs_root_ses (if set). This will prevent
@ses->dfs_root_ses of being put in the next call to cifs_put_smb_ses()
and thus potentially causing an use-after-free bug.
Fixes: 8e3554150d6c ("cifs: fix sharing of DFS connections") Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com> Signed-off-by: Steve French <stfrench@microsoft.com>