ksmbd: Fix to handle removal of rfc1002 header from smb_hdr

The commit that removed the RFC1002 header from struct smb_hdr didn't also
fix the places in ksmbd that use it in order to provide graceful rejection
of SMB1 protocol requests.

Fixes: 83bfbd0bb902 ("cifs: Remove the RFC1002 header from smb_hdr")
Reported-by: Namjae Jeon <[e-mail]>
Link: https://lore.kernel.org/r/CAKYAXd9Ju4MFkkH5Jxfi1mO0AWEr=[e-mail]/
Cc: ChenXiaoSong <[e-mail]>
Signed-off-by: David Howells <[e-mail]>
Signed-off-by: Namjae Jeon <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/server/server.c

···
 
 	if (ksmbd_conn_exiting(work->conn) ||
 	    ksmbd_conn_need_reconnect(work->conn)) {
-		rsp_hdr = work->response_buf;
+		rsp_hdr = smb2_get_msg(work->response_buf);
 		rsp_hdr->Status.CifsError = STATUS_CONNECTION_DISCONNECTED;
 		return 1;
 	}

fs/smb/server/smb_common.c

···
 	if (smb2_hdr->ProtocolId == SMB2_PROTO_NUMBER)
 		return ksmbd_smb2_check_message(work);
 
-	hdr = work->request_buf;
+	hdr = smb2_get_msg(work->request_buf);
 	if (*(__le32 *)hdr->Protocol == SMB1_PROTO_NUMBER &&
 	    hdr->Command == SMB_COM_NEGOTIATE) {
 		work->conn->outstanding_credits++;
···
 						  req->DialectCount);
 	}
 
-	proto = *(__le32 *)((struct smb_hdr *)buf)->Protocol;
 	if (proto == SMB1_PROTO_NUMBER) {
 		struct smb_negotiate_req *req;
 
-		req = (struct smb_negotiate_req *)buf;
+		req = (struct smb_negotiate_req *)smb2_get_msg(buf);
 		if (le16_to_cpu(req->ByteCount) < 2)
 			goto err_out;
 
-		if (offsetof(struct smb_negotiate_req, DialectsArray) - 4 +
+		if (offsetof(struct smb_negotiate_req, DialectsArray) +
 			le16_to_cpu(req->ByteCount) > smb_buf_length) {
 			goto err_out;
 		}
···
  */
 static int init_smb1_rsp_hdr(struct ksmbd_work *work)
 {
-	struct smb_hdr *rsp_hdr = (struct smb_hdr *)work->response_buf;
-	struct smb_hdr *rcv_hdr = (struct smb_hdr *)work->request_buf;
+	struct smb_hdr *rsp_hdr = (struct smb_hdr *)smb2_get_msg(work->response_buf);
+	struct smb_hdr *rcv_hdr = (struct smb_hdr *)smb2_get_msg(work->request_buf);
 
 	rsp_hdr->Command = SMB_COM_NEGOTIATE;
 	*(__le32 *)rsp_hdr->Protocol = SMB1_PROTO_NUMBER;
···
 
 int ksmbd_init_smb_server(struct ksmbd_conn *conn)
 {
+	struct smb_hdr *rcv_hdr = (struct smb_hdr *)smb2_get_msg(conn->request_buf);
 	__le32 proto;
 
-	proto = *(__le32 *)((struct smb_hdr *)conn->request_buf)->Protocol;
+	proto = *(__le32 *)rcv_hdr->Protocol;
 	if (conn->need_neg == false) {
 		if (proto == SMB1_PROTO_NUMBER)
 			return -EINVAL;
···
 
 static int smb_handle_negotiate(struct ksmbd_work *work)
 {
-	struct smb_negotiate_rsp *neg_rsp = work->response_buf;
+	struct smb_negotiate_rsp *neg_rsp = smb2_get_msg(work->response_buf);
 
 	ksmbd_debug(SMB, "Unsupported SMB1 protocol\n");
 
-	if (ksmbd_iov_pin_rsp(work, (void *)neg_rsp + 4,
-			      sizeof(struct smb_negotiate_rsp) - 4))
+	if (ksmbd_iov_pin_rsp(work, (void *)neg_rsp,
+			      sizeof(struct smb_negotiate_rsp)))
 		return -ENOMEM;
 
 	neg_rsp->hdr.Status.CifsError = STATUS_SUCCESS;