From d06ad5cfc8bf28ce6a6ebf5c0183fe9ed1583882 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 15 Dec 2023 10:12:11 +0100 Subject: [PATCH] mptcp: prevent tcp diag from closing listener subflows The MPTCP protocol does not expect that any other entity could change the first subflow status when such socket is listening. Unfortunately the TCP diag interface allows aborting any TCP socket, including MPTCP listeners subflows. As reported by syzbot, that trigger a WARN() and could lead to later bigger trouble. The MPTCP protocol needs to do some MPTCP-level cleanup actions to properly shutdown the listener. To keep the fix simple, prevent entirely the diag interface from stopping such listeners. We could refine the diag callback in a later, larger patch targeting net-next. Fixes: 57fc0f1ceaa4 ("mptcp: ensure listener is unhashed before updating the sk status") Closes: https://lore.kernel.org/netdev/0000000000004f4579060c68431b@google.com/ Reported-by: syzbot+5a01c3a666e726bc8752@syzkaller.appspotmail.com Signed-off-by: Paolo Abeni --- net/mptcp/subflow.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 7ca70dc785afe6..b84e28b7d5ee73 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1981,6 +1981,17 @@ static void tcp_release_cb_override(struct sock *ssk) tcp_release_cb(ssk); } +static int tcp_abort_override(struct sock *ssk, int err) +{ + /* closing a listener subflow requires a great deal of care. + * keep it simple and just prevent such operation + */ + if (inet_sk_state_load(ssk) == TCP_LISTEN) + return -EINVAL; + + return tcp_abort(ssk, err); +} + static struct tcp_ulp_ops subflow_ulp_ops __read_mostly = { .name = "mptcp", .owner = THIS_MODULE, @@ -2025,6 +2036,7 @@ void __init mptcp_subflow_init(void) tcp_prot_override = tcp_prot; tcp_prot_override.release_cb = tcp_release_cb_override; + tcp_prot_override.diag_destroy = tcp_abort_override; #if IS_ENABLED(CONFIG_MPTCP_IPV6) /* In struct mptcp_subflow_request_sock, we assume the TCP request sock @@ -2060,6 +2072,7 @@ void __init mptcp_subflow_init(void) tcpv6_prot_override = tcpv6_prot; tcpv6_prot_override.release_cb = tcp_release_cb_override; + tcpv6_prot_override.diag_destroy = tcp_abort_override; #endif mptcp_diag_subflow_init(&subflow_ulp_ops);