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

[Bartosz Chronowski]

#syz test: https://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)) {


On Mon, Aug 10, 2026 at 07:00:05AM -0700, syzbot wrote:
> Hello,
> 
> syzbot tried to test the proposed patch but the build/boot failed:
> 
> failed to checkout kernel repo git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git on commit a13307e97d5c54b65720bb71fa379960ded1e51a: failed to run ["git" "-c" "core.hooksPath=/dev/null" "fetch" "--force" "--tags" "f569e972c8e9057ee9c286220c83a480ebf30cc5" "a13307e97d5c54b65720bb71fa379960ded1e51a"]: exit status 128
> 
> 
> Tested on:
> 
> commit:         [unknown 
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git a13307e97d5c54b65720bb71fa379960ded1e51a
> kernel config:  https://syzkaller.appspot.com/x/.config?x=555131780f7c7272
> dashboard link: https://syzkaller.appspot.com/bug?extid=10a41dc44eef71aa9450
> compiler:       
> patch:          https://syzkaller.appspot.com/x/patch.diff?x=13c8a079580000
>