Re: [PATCH net v2 4/5] vsock: Do not reset a TCP_CLOSING socket

[Stefano Garzarella <sgarzare@redhat.com>]

On Tue, Sep 15, 2026 at 03:15:15PM +0200, Michal Luczaj wrote:
>Handle the previously overlooked TCP_ESTABLISHED -> TCP_CLOSING
>transition (on VIRTIO_VSOCK_OP_RST), which could race with the connect
>loop.
>
>Resetting a socket that is still present in connected_table can lead to
>memory corruption. The reporter noted lost transports for in-flight skbs,
>and I have reproduced crashes caused by re-insertion into connected_table.
>
>  list_add double add: new=, prev=, next=.
>  kernel BUG at lib/list_debug.c:35!
>  Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
>  Workqueue: vsock-loopback vsock_loopback_work
>  RIP: 0010:__list_add_valid_or_report+0x11f/0x130
>  Call Trace:
>   vsock_insert_connected.cold+0xe/0x13
>   virtio_transport_recv_pkt+0x10e9/0x1460
>   vsock_loopback_work+0x305/0x480
>   process_one_work+0xe4c/0x1560
>   worker_thread+0x4f1/0xd60
>   kthread+0x36e/0x470
>   ret_from_fork+0x47b/0x6b0
>   ret_from_fork_asm+0x1a/0x30
>
>Drop the redundant err=0 and the inaccurate comment above signal_pending().
>This fix is supplementary to commit 002541ef650b ("vsock: Ignore
>signal/timeout on connect() if already established"). Details under Link.
>
>Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
>Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
>Link: https://lore.kernel.org/netdev/anzT1fREOSyHT99k@v4bel/
>Signed-off-by: Michal Luczaj <mhal@rbox.co>
>---
> net/vmw_vsock/af_vsock.c | 20 +++++++++-----------
> 1 file changed, 9 insertions(+), 11 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 499e902becfa..adf3f018347e 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1712,7 +1712,6 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
> 	long timeout;
> 	DEFINE_WAIT(wait);
>
>-	err = 0;
> 	sk = sock->sk;
> 	vsk = vsock_sk(sk);
>
>@@ -1834,23 +1833,22 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
> 		timeout = schedule_timeout(timeout);
> 		lock_sock(sk);
>
>-		/* Connection established. Whatever happens to socket once we
>-		 * release it, that's not connect()'s concern. No need to go
>+		/* Connection was established. Whatever happens to socket once
>+		 * we release it, that's not connect()'s concern. No need to go
> 		 * into signal and timeout handling. Call it a day.
> 		 *
> 		 * Note that allowing to "reset" an already established socket
> 		 * here is racy and insecure.
> 		 */
>-		if (sk->sk_state == TCP_ESTABLISHED)
>-			break;
>+		if (sk->sk_state == TCP_ESTABLISHED ||
>+		    sk->sk_state == TCP_CLOSING) {
>+			err = 0;
>+			goto out_wait;
>+		}
>
> 		/* If connection was _not_ established and a signal/timeout came
> 		 * to be, we want the socket's state reset. User space may want
> 		 * to retry.
>-		 *
>-		 * sk_state != TCP_ESTABLISHED implies that socket is not on
>-		 * vsock_connected_table. We keep the binding and the transport
>-		 * assigned.

Should we keep "We keep the binding and the transport assigned." or 
maybe add on the other phrase, "User space may want to retry, so we keep 
..."

> 		 */
> 		if (signal_pending(current) || timeout == 0) {
> 			err = timeout == 0 ? -ETIMEDOUT : sock_intr_errno(timeout);
>@@ -1874,8 +1872,8 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr,
> 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
> 	}
>
>-	err = sock_error(sk);
>-	if (err) {

Should we add a comment here explaining why we are doing this?

Thanks,
Stefano

>+	if (sk->sk_state != TCP_ESTABLISHED && sk->sk_state != TCP_CLOSING) {
>+		err = sock_error(sk);
> 		sk->sk_state = TCP_CLOSE;
> 		sock->state = SS_UNCONNECTED;
> 	}
>
>-- 
>2.55.0
>