From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590084; b=gsbImD3NcRMkBerrGpKZ+gXA+3T8Fx+l0JhksVZ8qCQFmEBFqep4/fNywuWx8dDpiOiz cMI8XtIHySmhcLbrMEsuEeNqCny7TiPZk5HW775agIyW9VqpRwAakgsVbWKNYIArcLU2R VFitHpnyfTgFEoQOD5k14NTdzJ7dlEvF3HN0bpfIBZ7lytH5r+22FWppYK5dCGht5HJ/d qePbUjLfYUw6veWfeaZ1JrC31ZOgw654GZrnLQpkAD3VbKuTB9bVZK34Cjl74gafWNb7C 1FlsA3QmVa3VmzRZzfdoSyS4wAYdv8f2jaYMaEFaF3gYvjKTSrDLD60gP1qTqru+D/A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590084; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=5HPH8BokxfOEGyGVqKIrAArrKT7488pG4FTnFfuLVPg=; b=KmjVoUJFcPfAUC22sTFWbkQh/YRb8T6eCKzKK8+Y2g4G6iMQ1afWb43HnWzr+oKOQnON ungJM8kaKnJ5fsfzeb2gPuBZaoDRB58UtD6d3Y2MZUhhS1R5zDXsj9ez8oBRIhvhzF0f4 ZKxsdMl1OsFY/B1vJAarOK/lTTCPLwCbSWbBWCVWfMYW3K3aTJonxiROzTuXYjo+98RQI CGlhwYPz9bV6CZk7jGbh+EKHuj5vMTAudfBzlfe6rLL3YkXTKAxYzln9ytfiFrpPZ87CD zd315Q/HpfDVpUCK21fL95AL9I+Ca0Pio+ezaWNN4nTMwepECGF9LF5UVYgYghCa3oA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=j565eZnj; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0077606A32E; Fri, 13 Nov 2026 17:14:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=j565eZnj Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4CD941F000C5; Fri, 13 Nov 2026 17:14:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590084; bh=5HPH8BokxfOEGyGVqKIrAArrKT7488pG4FTnFfuLVPg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=j565eZnj5aFqzrpAUf/vZT5bjOPTTOXEXYeOmWcKiW44ljdGt+WefX0SHDBELtYnv zG/AdHXmdmz4SvAvHRyD/SwkbjuVT3CQNb7vlUVY4xxG80DE645azh15AWDOB4W68V eWgfRyQ2mP/LUYX75UUkDyJkOuZYl7xpn/eJCtvM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bernard Pidoux , Sasha Levin Subject: [PATCH 6.18 112/686] ax25: free a closed socket when its device goes down Date: Fri, 13 Nov 2026 10:44:05 -0500 Message-ID: <20261113153824.639302559@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bernard Pidoux A SOCK_SEQPACKET socket closed by its owner is marked SOCK_DESTROY and left to its heartbeat, which calls ax25_destroy_socket() once the link is down. A connection that a listener never accepted gets the same treatment when the listener is closed (TCP_LISTEN and SOCK_DEAD). Neither socket has a struct socket left, so nothing else frees it. If the device goes away during that time, ax25_kill_by_device() calls ax25_disconnect() with ENETUNREACH, which since commit fc6d01ff9ef0 ("ax25: Fix NULL pointer dereferences in ax25 timers") stops the heartbeat with timer_delete_sync() whatever the socket state, and then takes the control block off the list. The socket is never freed and keeps a reference on the ax25 module, so ax25 can no longer be unloaded. This shows up on a node that closes a connection and restarts kissattach, or unloads bpqether, within the few seconds the heartbeat needs: each such connection adds one to the ax25 module refcount for good. Free those sockets in ax25_kill_by_device() with ax25_destroy_socket(), under the same condition the heartbeat uses. Tested on a QEMU bench (6.12.94 with KASAN and lockdep, two guests over a KISS serial link): three client connections closed and ax0 removed one second later, then a connection left unaccepted by a closed listener and ax0 removed one second later. ax25 refcount after each: before after 3 closed clients +3 0 unaccepted connection +1 0 control (ax0 removed 0 0 25 s after close) Same result over five runs, with no KASAN or lockdep report. Also seen on two live nodes over bpqether, where ax25 could no longer be reloaded until a reboot. Fixes: fc6d01ff9ef0 ("ax25: Fix NULL pointer dereferences in ax25 timers") Signed-off-by: Bernard Pidoux Assisted-by: Claude:claude-opus-5-5 (cherry picked from commit 2e9cb81885fefea3690a9b94b9ff5ebf761bea73) Signed-off-by: Sasha Levin --- net/ax25/af_ax25.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 5ce59d1ba8221..63fe99746d328 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -78,6 +78,7 @@ static void ax25_kill_by_device(struct net_device *dev) ax25_dev *ax25_dev; ax25_cb *s; struct sock *sk; + bool orphan; if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) return; @@ -109,6 +110,16 @@ static void ax25_kill_by_device(struct net_device *dev) sock_hold(sk); spin_unlock_bh(&ax25_list_lock); lock_sock(sk); + /* + * A socket closed by its owner, or a connection left + * unaccepted by a closed listener, is freed by its + * heartbeat once it is down. ax25_disconnect() below + * stops that heartbeat for good, so free the socket + * here, or it is never freed and pins the module. + */ + orphan = sock_flag(sk, SOCK_DESTROY) || + (sk->sk_state == TCP_LISTEN && + sock_flag(sk, SOCK_DEAD)); ax25_disconnect(s, ENETUNREACH); WRITE_ONCE(s->ax25_dev, NULL); if (sk->sk_socket) { @@ -116,7 +127,10 @@ static void ax25_kill_by_device(struct net_device *dev) &s->dev_tracker); ax25_dev_put(ax25_dev); } - ax25_cb_del(s); + if (orphan) + ax25_destroy_socket(s); + else + ax25_cb_del(s); release_sock(sk); spin_lock_bh(&ax25_list_lock); sock_put(sk); -- 2.53.0