From nobody Tue Jun 23 09:23:52 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2432C433F5 for ; Tue, 8 Mar 2022 08:14:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344878AbiCHIPd (ORCPT ); Tue, 8 Mar 2022 03:15:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39620 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241091AbiCHIP1 (ORCPT ); Tue, 8 Mar 2022 03:15:27 -0500 Received: from zju.edu.cn (mail.zju.edu.cn [61.164.42.155]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3BB69B864; Tue, 8 Mar 2022 00:12:44 -0800 (PST) Received: from ubuntu.localdomain (unknown [10.15.192.164]) by mail-app4 (Coremail) with SMTP id cS_KCgC3L3PoDydiMv1CAA--.28839S2; Tue, 08 Mar 2022 16:12:29 +0800 (CST) From: Duoming Zhou To: linux-hams@vger.kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kuba@kernel.org, davem@davemloft.net, ralf@linux-mips.org, jreuter@yaina.de, Duoming Zhou Subject: [PATCH] ax25: Fix NULL pointer dereference in ax25_kill_by_device Date: Tue, 8 Mar 2022 16:12:23 +0800 Message-Id: <20220308081223.15919-1-duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 X-CM-TRANSID: cS_KCgC3L3PoDydiMv1CAA--.28839S2 X-Coremail-Antispam: 1UD129KBjvJXoW7CF1xtry5Aw4rCFyUuF15Arb_yoW8Cw1DpF Z0k34fGrW7J34UCrs7GF18JF1UuF4qq3y5WF10vFy7C3s8Jr95trZ5trWUW3y3CF4rAFWU Za47J3y8Xa1UZaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkI1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVWxJr0_GcWl84ACjcxK6I8E 87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_GcCE3s1le2I262IYc4CY6c 8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_ Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwI xGrwACjI8F5VA0II8E6IAqYI8I648v4I1l42xK82IYc2Ij64vIr41l42xK82IY6x8ErcxF aVAv8VW8uw4UJr1UMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr 4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxG rwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVWUJVW8Jw CI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2 z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7VUbXdbUUUUUU== X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/1tbiAgMDAVZdtYj89QAFs5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" When two ax25 devices attempted to establish connection, the requester use = ax25_create(), ax25_bind() and ax25_connect() to initiate connection. The receiver use ax2= 5_rcv() to accept connection and use ax25_create_cb() in ax25_rcv() to create ax25_cb,= but the ax25_cb->sk is NULL. When the receiver is detaching, a NULL pointer derefer= ence bug caused by sock_hold(sk) in ax25_kill_by_device() will happen. The correspon= ding fail log is shown below: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BUG: KASAN: null-ptr-deref in ax25_device_event+0xfd/0x290 Call Trace: ... ax25_device_event+0xfd/0x290 raw_notifier_call_chain+0x5e/0x70 dev_close_many+0x174/0x220 unregister_netdevice_many+0x1f7/0xa60 unregister_netdevice_queue+0x12f/0x170 unregister_netdev+0x13/0x20 mkiss_close+0xcd/0x140 tty_ldisc_release+0xc0/0x220 tty_release_struct+0x17/0xa0 tty_release+0x62d/0x670 ... This patch add condition check in ax25_kill_by_device(). If s->sk is NULL, it will goto if branch to kill device. Fixes: 4e0f718daf97 ("ax25: improve the incomplete fix to avoid UAF and NPD= bugs") Reported-by: Thomas Osterried Signed-off-by: Duoming Zhou --- net/ax25/af_ax25.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index d53cbb4e250..6bd09718077 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -87,6 +87,13 @@ static void ax25_kill_by_device(struct net_device *dev) ax25_for_each(s, &ax25_list) { if (s->ax25_dev =3D=3D ax25_dev) { sk =3D s->sk; + if (!sk) { + spin_unlock_bh(&ax25_list_lock); + s->ax25_dev =3D NULL; + ax25_disconnect(s, ENETUNREACH); + spin_lock_bh(&ax25_list_lock); + goto again; + } sock_hold(sk); spin_unlock_bh(&ax25_list_lock); lock_sock(sk); -- 2.17.1