cifs: parse_dfs_referrals: prevent oob on malformed input

Malicious SMB server can send invalid reply to FSCTL_DFS_GET_REFERRALS

- reply smaller than sizeof(struct get_dfs_referral_rsp)
- reply with number of referrals smaller than NumberOfReferrals in the
header

Processing of such replies will cause oob.

Return -EINVAL error on such replies to prevent oob-s.

Signed-off-by: Eugene Korenevsky <ekorenevsky@aliyun.com>
Cc: stable@vger.kernel.org
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Steve French <stfrench@microsoft.com>