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[69.172.89.235]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35fb87d0361sm1120992a91.0.2026.04.13.01.52.46 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 13 Apr 2026 01:52:48 -0700 (PDT) From: Dudu Lu To: netdev@vger.kernel.org Cc: stefanha@redhat.com, sgarzare@redhat.com, mst@redhat.com, jasowang@redhat.com, Dudu Lu Subject: [PATCH] vsock/virtio: fix accept queue count leak on transport mismatch in recv_listen Date: Mon, 13 Apr 2026 16:52:43 +0800 Message-Id: <20260413085243.73200-1-phx0fer@gmail.com> X-Mailer: git-send-email 2.39.3 (Apple Git-145) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit virtio_transport_recv_listen() calls sk_acceptq_added(sk) to increment the listener's accept queue counter before calling vsock_assign_transport(). When vsock_assign_transport() fails or selects a different transport than the one that received the packet, the error path returns without calling sk_acceptq_removed(sk), permanently incrementing sk_ack_backlog. A malicious VM peer can exploit this by sending repeated CONNECT requests that trigger the transport mismatch condition. Each such request permanently increments sk_ack_backlog. After approximately backlog+1 such requests (default backlog ~128), sk_acceptq_is_full() returns true, causing the listener to reject ALL new connections with -ENOMEM. The only recovery is closing and re-creating the listener socket. Compare with vmci_transport.c and hyperv_transport.c which correctly place sk_acceptq_added() AFTER the transport check, avoiding this issue entirely. Fix by moving sk_acceptq_added(sk) to after the transport validation check, matching the pattern used by the other transports. Fixes: c0cfa2d8a788 ("vsock: add multi-transports support") Signed-off-by: Dudu Lu --- net/vmw_vsock/virtio_transport_common.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index 8a9fb23c6e85..29e1d9833be4 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -1,3 +1,4 @@ + sk_acceptq_added(sk); // SPDX-License-Identifier: GPL-2.0-only /* * common code for virtio vsock @@ -1560,8 +1561,9 @@ virtio_transport_recv_listen(struct sock *sk, struct sk_buff *skb, return -ENOMEM; } - sk_acceptq_added(sk); + + sk_acceptq_added(sk); lock_sock_nested(child, SINGLE_DEPTH_NESTING); child->sk_state = TCP_ESTABLISHED; -- 2.39.3 (Apple Git-145)