6.6-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Abeni pabeni@redhat.com
commit 4c0288299fd09ee7c6fbe2f57421f314d8c981db upstream.
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") Cc: stable@vger.kernel.org Reported-by: syzbot+5a01c3a666e726bc8752@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/0000000000004f4579060c68431b@google.com/ Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts matttbe@kernel.org Link: https://lore.kernel.org/r/20231226-upstream-net-20231226-mptcp-prevent-warn-... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/subflow.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
--- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1974,6 +1974,17 @@ static void tcp_release_cb_override(stru 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, @@ -2018,6 +2029,7 @@ 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 @@ -2054,6 +2066,7 @@ 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);