From nobody Wed Feb 11 05:11:13 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1763787282517102.77567129592228; Fri, 21 Nov 2025 20:54:42 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vMcyy-00040X-7Y; Fri, 21 Nov 2025 21:04:13 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMc90-00063R-Es; Fri, 21 Nov 2025 20:10:30 -0500 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMc6x-0003ud-WA; Fri, 21 Nov 2025 20:10:26 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 2B07416CA6B; Fri, 21 Nov 2025 21:44:26 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id DD8BF321CA7; Fri, 21 Nov 2025 21:44:34 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Eric Blake , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Michael Tokarev Subject: [Stable-10.0.7 48/81] qio: Unwatch before notify in QIONetListener Date: Fri, 21 Nov 2025 21:43:47 +0300 Message-ID: <20251121184424.1137669-48-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1763787283378018901 From: Eric Blake When changing the callback registered with QIONetListener, the code was calling notify on the old opaque data prior to actually removing the old GSource objects still pointing to that data. Similarly, during finalize, it called notify before tearing down the various GSource objects tied to the data. In practice, a grep of the QEMU code base found that every existing client of QIONetListener passes in a NULL notifier (the opaque data, if non-NULL, outlives the NetListener and so does not need cleanup when the NetListener is torn down), so this patch has no impact. And even if a caller had passed in a reference-counted object with a notifier of object_unref but kept its own reference on the data, then the early notify would merely reduce a refcount from (say) 2 to 1, but not free the object. However, it is a latent bug waiting to bite any future caller that passes in data where the notifier actually frees the object, because the GSource could then trigger a use-after-free if it loses the race on a last-minute client connection resulting in the data being passed to one final use of the async callback. Better is to delay the notify call until after all GSource that have been given a copy of the opaque data are torn down. CC: qemu-stable@nongnu.org Fixes: 530473924d "io: introduce a network socket listener API", v2.12.0 Signed-off-by: Eric Blake Reviewed-by: Daniel P. Berrang=C3=A9 Message-ID: <20251113011625.878876-18-eblake@redhat.com> (cherry picked from commit 6e03d5cdc991f5db86969fc6aeaca96234426263) Signed-off-by: Michael Tokarev diff --git a/io/net-listener.c b/io/net-listener.c index 007acbd5b1..d71b65270e 100644 --- a/io/net-listener.c +++ b/io/net-listener.c @@ -148,13 +148,6 @@ void qio_net_listener_set_client_func_full(QIONetListe= ner *listener, =20 trace_qio_net_listener_unwatch(listener, listener->io_func, "set_client_func"); - if (listener->io_notify) { - listener->io_notify(listener->io_data); - } - listener->io_func =3D func; - listener->io_data =3D data; - listener->io_notify =3D notify; - for (i =3D 0; i < listener->nsioc; i++) { if (listener->io_source[i]) { g_source_destroy(listener->io_source[i]); @@ -163,6 +156,13 @@ void qio_net_listener_set_client_func_full(QIONetListe= ner *listener, } } =20 + if (listener->io_notify) { + listener->io_notify(listener->io_data); + } + listener->io_func =3D func; + listener->io_data =3D data; + listener->io_notify =3D notify; + trace_qio_net_listener_watch(listener, listener->io_func, "set_client_func"); if (listener->io_func !=3D NULL) { @@ -300,10 +300,10 @@ static void qio_net_listener_finalize(Object *obj) QIONetListener *listener =3D QIO_NET_LISTENER(obj); size_t i; =20 + qio_net_listener_disconnect(listener); if (listener->io_notify) { listener->io_notify(listener->io_data); } - qio_net_listener_disconnect(listener); =20 for (i =3D 0; i < listener->nsioc; i++) { object_unref(OBJECT(listener->sioc[i])); --=20 2.47.3