smb: server: let recv_done() avoid touching data_transfer after cleanup/move

Calling enqueue_reassembly() and wake_up_interruptible(&t->wait_reassembly_queue)
or put_receive_buffer() means the recvmsg/data_transfer pointer might
get re-used by another thread, which means these should be
the last operations before calling return.

Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Fixes: 0626e66 ("cifsd: add server handler for central processing and tranport layers")
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: metze-samba

fs/smb/server/transport_rdma.c

@@ -581,16 +581,11 @@ static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
 			else
 				t->full_packet_received = true;
 
-			enqueue_reassembly(t, recvmsg, (int)data_length);
-			wake_up_interruptible(&t->wait_reassembly_queue);
-
 			spin_lock(&t->receive_credit_lock);
 			receive_credits = --(t->recv_credits);
 			avail_recvmsg_count = t->count_avail_recvmsg;
 			spin_unlock(&t->receive_credit_lock);
 		} else {
-			put_recvmsg(t, recvmsg);
-
 			spin_lock(&t->receive_credit_lock);
 			receive_credits = --(t->recv_credits);
 			avail_recvmsg_count = ++(t->count_avail_recvmsg);
@@ -612,6 +607,13 @@ static void recv_done(struct ib_cq *cq, struct ib_wc *wc)
 		if (is_receive_credit_post_required(receive_credits, avail_recvmsg_count))
 			mod_delayed_work(smb_direct_wq,
 					 &t->post_recv_credits_work, 0);
+
+		if (data_length) {
+			enqueue_reassembly(t, recvmsg, (int)data_length);
+			wake_up_interruptible(&t->wait_reassembly_queue);
+		} else
+			put_recvmsg(t, recvmsg);
+
 		return;
 	}
 	}