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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , Andy King , George Zhang , Dmitry Torokhov , "K . Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Stefan Hajnoczi , "Michael S . Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Bryan Tan , Vishnu Dasa , bcm-kernel-feedback-list@broadcom.com, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, baijiaju1990@gmail.com, r33s3n6@gmail.com, gality369@gmail.com, zhenghaoran154@gmail.com, hanguidong02@gmail.com, zzzccc427@gmail.com, Ziyu Zhang Subject: [PATCH net v2] vsock: keep poll shutdown state consistent Date: Wed, 20 May 2026 00:56:36 +0800 Message-Id: <20260519165636.62542-1-ziyuzhang201@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" vsock_poll() reads vsk->peer_shutdown before taking the socket lock to set EPOLLHUP and EPOLLRDHUP, then reads it again after taking the lock to report EOF readability. A shutdown packet can update peer_shutdown while poll is waiting for the lock, so one poll invocation can report EOF readability without the corresponding HUP/RDHUP bits. For connectible sockets, take one peer_shutdown snapshot after lock_sock() and use it for all peer-shutdown-derived poll bits. For datagram sockets, which do not take lock_sock() in poll(), take one lockless READ_ONCE() snapshot and pair it with WRITE_ONCE() on the writer side. This keeps the peer-shutdown-derived bits internally consistent for each poll pass. Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") Signed-off-by: Ziyu Zhang --- Link: https://lore.kernel.org/netdev/20260516034745.260442-1-ziyuzhang201@g= mail.com/ v2: - Pair lockless READ_ONCE() users with WRITE_ONCE() on peer_shutdown writer= s. - Move datagram shutdown handling into the SOCK_DGRAM branch and add a comm= ent. - Keep one connectible peer_shutdown snapshot after lock_sock() and restore the previous shutdown-derived mask ordering. net/vmw_vsock/af_vsock.c | 49 ++++++++++++++++--------- net/vmw_vsock/hyperv_transport.c | 9 +++-- net/vmw_vsock/virtio_transport_common.c | 14 ++++--- net/vmw_vsock/vmci_transport.c | 8 ++-- 4 files changed, 52 insertions(+), 28 deletions(-) diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index adcba1b7b..789b00f6e 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -523,7 +523,7 @@ int vsock_assign_transport(struct vsock_sock *vsk, stru= ct vsock_sock *psk) */ sock_reset_flag(sk, SOCK_DONE); sk->sk_state =3D TCP_CLOSE; - vsk->peer_shutdown =3D 0; + WRITE_ONCE(vsk->peer_shutdown, 0); } =20 if (sk->sk_type =3D=3D SOCK_SEQPACKET) { @@ -814,7 +814,7 @@ static struct sock *__vsock_create(struct net *net, vsk->rejected =3D false; vsk->sent_request =3D false; vsk->ignore_connecting_rst =3D false; - vsk->peer_shutdown =3D 0; + WRITE_ONCE(vsk->peer_shutdown, 0); INIT_DELAYED_WORK(&vsk->connect_work, vsock_connect_timeout); INIT_DELAYED_WORK(&vsk->pending_work, vsock_pending_work); =20 @@ -1122,6 +1122,25 @@ static int vsock_shutdown(struct socket *sock, int m= ode) return err; } =20 +static __poll_t vsock_poll_shutdown(struct sock *sk, u32 peer_shutdown) +{ + __poll_t mask =3D 0; + + /* INET sockets treat local write shutdown and peer write shutdown as a + * case of EPOLLHUP set. + */ + if (sk->sk_shutdown =3D=3D SHUTDOWN_MASK || + ((sk->sk_shutdown & SEND_SHUTDOWN) && + (peer_shutdown & SEND_SHUTDOWN))) + mask |=3D EPOLLHUP; + + if (sk->sk_shutdown & RCV_SHUTDOWN || + peer_shutdown & SEND_SHUTDOWN) + mask |=3D EPOLLRDHUP; + + return mask; +} + static __poll_t vsock_poll(struct file *file, struct socket *sock, poll_table *wait) { @@ -1139,24 +1158,17 @@ static __poll_t vsock_poll(struct file *file, struc= t socket *sock, /* Signify that there has been an error on this socket. */ mask |=3D EPOLLERR; =20 - /* INET sockets treat local write shutdown and peer write shutdown as a - * case of EPOLLHUP set. - */ - if ((sk->sk_shutdown =3D=3D SHUTDOWN_MASK) || - ((sk->sk_shutdown & SEND_SHUTDOWN) && - (vsk->peer_shutdown & SEND_SHUTDOWN))) { - mask |=3D EPOLLHUP; - } - - if (sk->sk_shutdown & RCV_SHUTDOWN || - vsk->peer_shutdown & SEND_SHUTDOWN) { - mask |=3D EPOLLRDHUP; - } - if (sk_is_readable(sk)) mask |=3D EPOLLIN | EPOLLRDNORM; =20 if (sock->type =3D=3D SOCK_DGRAM) { + u32 peer_shutdown =3D READ_ONCE(vsk->peer_shutdown); + + /* DGRAM sockets do not take lock_sock() in poll(), so use one + * lockless snapshot for all shutdown-derived mask bits. + */ + mask |=3D vsock_poll_shutdown(sk, peer_shutdown); + /* For datagram sockets we can read if there is something in * the queue and write as long as the socket isn't shutdown for * sending. @@ -1171,6 +1183,7 @@ static __poll_t vsock_poll(struct file *file, struct = socket *sock, =20 } else if (sock_type_connectible(sk->sk_type)) { const struct vsock_transport *transport; + u32 peer_shutdown; =20 lock_sock(sk); =20 @@ -1203,8 +1216,10 @@ static __poll_t vsock_poll(struct file *file, struct= socket *sock, * terminated should also be considered read, and we check the * shutdown flag for that. */ + peer_shutdown =3D READ_ONCE(vsk->peer_shutdown); + mask |=3D vsock_poll_shutdown(sk, peer_shutdown); if (sk->sk_shutdown & RCV_SHUTDOWN || - vsk->peer_shutdown & SEND_SHUTDOWN) { + peer_shutdown & SEND_SHUTDOWN) { mask |=3D EPOLLIN | EPOLLRDNORM; } =20 diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transp= ort.c index 432fcbbd1..16b981566 100644 --- a/net/vmw_vsock/hyperv_transport.c +++ b/net/vmw_vsock/hyperv_transport.c @@ -264,7 +264,7 @@ static void hvs_do_close_lock_held(struct vsock_sock *v= sk, struct sock *sk =3D sk_vsock(vsk); =20 sock_set_flag(sk, SOCK_DONE); - vsk->peer_shutdown =3D SHUTDOWN_MASK; + WRITE_ONCE(vsk->peer_shutdown, SHUTDOWN_MASK); if (vsock_stream_has_data(vsk) <=3D 0) sk->sk_state =3D TCP_CLOSING; sk->sk_state_change(sk); @@ -593,7 +593,9 @@ static int hvs_update_recv_data(struct hvsock *hvs) return -EIO; =20 if (payload_len =3D=3D 0) - hvs->vsk->peer_shutdown |=3D SEND_SHUTDOWN; + WRITE_ONCE(hvs->vsk->peer_shutdown, + READ_ONCE(hvs->vsk->peer_shutdown) | + SEND_SHUTDOWN); =20 hvs->recv_data_len =3D payload_len; hvs->recv_data_off =3D 0; @@ -715,7 +717,8 @@ static s64 hvs_stream_has_data(struct vsock_sock *vsk) return ret; return hvs->recv_data_len; case 0: - vsk->peer_shutdown |=3D SEND_SHUTDOWN; + WRITE_ONCE(vsk->peer_shutdown, + READ_ONCE(vsk->peer_shutdown) | SEND_SHUTDOWN); ret =3D 0; break; default: /* -1 */ diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio= _transport_common.c index dcc8a1d58..71d8eac82 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -1220,7 +1220,7 @@ static void virtio_transport_do_close(struct vsock_so= ck *vsk, struct sock *sk =3D sk_vsock(vsk); =20 sock_set_flag(sk, SOCK_DONE); - vsk->peer_shutdown =3D SHUTDOWN_MASK; + WRITE_ONCE(vsk->peer_shutdown, SHUTDOWN_MASK); if (vsock_stream_has_data(vsk) <=3D 0) sk->sk_state =3D TCP_CLOSING; sk->sk_state_change(sk); @@ -1411,12 +1411,15 @@ virtio_transport_recv_connected(struct sock *sk, case VIRTIO_VSOCK_OP_CREDIT_UPDATE: sk->sk_write_space(sk); break; - case VIRTIO_VSOCK_OP_SHUTDOWN: + case VIRTIO_VSOCK_OP_SHUTDOWN: { + u32 peer_shutdown =3D READ_ONCE(vsk->peer_shutdown); + if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SHUTDOWN_RCV) - vsk->peer_shutdown |=3D RCV_SHUTDOWN; + peer_shutdown |=3D RCV_SHUTDOWN; if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SHUTDOWN_SEND) - vsk->peer_shutdown |=3D SEND_SHUTDOWN; - if (vsk->peer_shutdown =3D=3D SHUTDOWN_MASK) { + peer_shutdown |=3D SEND_SHUTDOWN; + WRITE_ONCE(vsk->peer_shutdown, peer_shutdown); + if (peer_shutdown =3D=3D SHUTDOWN_MASK) { if (vsock_stream_has_data(vsk) <=3D 0 && !sock_flag(sk, SOCK_DONE)) { (void)virtio_transport_reset(vsk, NULL); virtio_transport_do_close(vsk, true); @@ -1431,6 +1434,7 @@ virtio_transport_recv_connected(struct sock *sk, if (le32_to_cpu(virtio_vsock_hdr(skb)->flags)) sk->sk_state_change(sk); break; + } case VIRTIO_VSOCK_OP_RST: virtio_transport_do_close(vsk, true); break; diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c index 7eccd6708..c2231c402 100644 --- a/net/vmw_vsock/vmci_transport.c +++ b/net/vmw_vsock/vmci_transport.c @@ -811,7 +811,7 @@ static void vmci_transport_handle_detach(struct sock *s= k) /* On a detach the peer will not be sending or receiving * anymore. */ - vsk->peer_shutdown =3D SHUTDOWN_MASK; + WRITE_ONCE(vsk->peer_shutdown, SHUTDOWN_MASK); =20 /* We should not be sending anymore since the peer won't be * there to receive, but we can still receive if there is data @@ -1534,7 +1534,9 @@ static int vmci_transport_recv_connected(struct sock = *sk, if (pkt->u.mode) { vsk =3D vsock_sk(sk); =20 - vsk->peer_shutdown |=3D pkt->u.mode; + WRITE_ONCE(vsk->peer_shutdown, + READ_ONCE(vsk->peer_shutdown) | + pkt->u.mode); sk->sk_state_change(sk); } break; @@ -1551,7 +1553,7 @@ static int vmci_transport_recv_connected(struct sock = *sk, * a clean shutdown. */ sock_set_flag(sk, SOCK_DONE); - vsk->peer_shutdown =3D SHUTDOWN_MASK; + WRITE_ONCE(vsk->peer_shutdown, SHUTDOWN_MASK); if (vsock_stream_has_data(vsk) <=3D 0) sk->sk_state =3D TCP_CLOSING; =20 --=20 2.43.0