Forwarded: Re: [syzbot] [tipc?] BUG: soft lockup in do_sock_setsockopt

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Subject: Re: [syzbot] [tipc?] BUG: soft lockup in do_sock_setsockopt
Author: immersa.bartosz.chronowski@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git a13307e97d5c54b65720bb71fa379960ded1e51a

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index d5d70eb230b5..f3c4bccaadc8 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -156,7 +156,8 @@ static int tipc_sk_insert(struct tipc_sock *tsk);
 static void tipc_sk_remove(struct tipc_sock *tsk);
 static int __tipc_sendstream(struct socket *sock, struct msghdr *m, size_t dsz);
 static int __tipc_sendmsg(struct socket *sock, struct msghdr *m, size_t dsz);
-static void tipc_sk_push_backlog(struct tipc_sock *tsk, bool nagle_ack);
+static void tipc_sk_push_backlog(struct tipc_sock *tsk, bool nagle_ack,
+				 struct sk_buff_head *xmitq);
 static int tipc_wait_for_connect(struct socket *sock, long *timeo_p);
 
 static const struct proto_ops packet_ops;
@@ -561,7 +562,7 @@ static void __tipc_shutdown(struct socket *sock, int error)
 					    !tsk_conn_cong(tsk)));
 
 	/* Push out delayed messages if in Nagle mode */
-	tipc_sk_push_backlog(tsk, false);
+	tipc_sk_push_backlog(tsk, false, NULL);
 	/* Remove pending SYN */
 	__skb_queue_purge(&sk->sk_write_queue);
 
@@ -1268,8 +1269,10 @@ void tipc_sk_mcast_rcv(struct net *net, struct sk_buff_head *arrvq,
 
 /* tipc_sk_push_backlog(): send accumulated buffers in socket write queue
  *                         when socket is in Nagle mode
+ * @xmitq: receive output queue, or NULL outside receive context
  */
-static void tipc_sk_push_backlog(struct tipc_sock *tsk, bool nagle_ack)
+static void tipc_sk_push_backlog(struct tipc_sock *tsk, bool nagle_ack,
+				 struct sk_buff_head *xmitq)
 {
 	struct sk_buff_head *txq = &tsk->sk.sk_write_queue;
 	struct sk_buff *skb = skb_peek_tail(txq);
@@ -1311,6 +1314,10 @@ static void tipc_sk_push_backlog(struct tipc_sock *tsk, bool nagle_ack)
 		tsk->pkt_cnt += skb_queue_len(txq);
 	tsk->snt_unacked += tsk->snd_backlog;
 	tsk->snd_backlog = 0;
+	if (xmitq && in_own_node(net, dnode)) {
+		skb_queue_splice_tail_init(txq, xmitq);
+		return;
+	}
 	rc = tipc_node_xmit(net, txq, dnode, tsk->portid);
 	if (rc == -ELINKCONG)
 		tsk->cong_link_cnt = 1;
@@ -1368,7 +1375,7 @@ static void tipc_sk_conn_proto_rcv(struct tipc_sock *tsk, struct sk_buff *skb,
 			goto exit;
 
 		was_cong = tsk_conn_cong(tsk);
-		tipc_sk_push_backlog(tsk, msg_nagle_ack(hdr));
+		tipc_sk_push_backlog(tsk, msg_nagle_ack(hdr), xmitq);
 		tsk->snt_unacked -= msg_conn_ack(hdr);
 		if (tsk->peer_caps & TIPC_BLOCK_FLOWCTL)
 			tsk->snd_win = msg_adv_win(hdr);
@@ -2166,7 +2173,7 @@ static void tipc_sk_proto_rcv(struct sock *sk,
 		smp_wmb();
 		tsk->cong_link_cnt--;
 		wakeup = true;
-		tipc_sk_push_backlog(tsk, false);
+		tipc_sk_push_backlog(tsk, false, xmitq);
 		break;
 	case GROUP_PROTOCOL:
 		tipc_group_proto_rcv(grp, &wakeup, hdr, inputq, xmitq);
@@ -2257,7 +2264,7 @@ static bool tipc_sk_filter_connect(struct tipc_sock *tsk, struct sk_buff *skb,
 		return false;
 	case TIPC_ESTABLISHED:
 		if (!skb_queue_empty(&sk->sk_write_queue))
-			tipc_sk_push_backlog(tsk, false);
+			tipc_sk_push_backlog(tsk, false, xmitq);
 		/* Accept only connection-based messages sent by peer */
 		if (likely(con_msg && !err && pport == oport &&
 			   pnode == onode)) {