From patchwork Thu Mar 10 12:06:40 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Duoming Zhou X-Patchwork-Id: 12776242 X-Patchwork-Delegate: kuba@kernel.org 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 F36A3C433F5 for ; Thu, 10 Mar 2022 12:07:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234298AbiCJMIQ (ORCPT ); Thu, 10 Mar 2022 07:08:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43832 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240407AbiCJMIB (ORCPT ); Thu, 10 Mar 2022 07:08:01 -0500 Received: from zju.edu.cn (spam.zju.edu.cn [61.164.42.155]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E255114077C; Thu, 10 Mar 2022 04:06:57 -0800 (PST) Received: from ubuntu.localdomain (unknown [10.15.192.164]) by mail-app4 (Coremail) with SMTP id cS_KCgDnCUnR6Sliw8BjAA--.3672S2; Thu, 10 Mar 2022 20:06:47 +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 dereferences in ax25 timers Date: Thu, 10 Mar 2022 20:06:40 +0800 Message-Id: <20220310120640.43269-1-duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 X-CM-TRANSID: cS_KCgDnCUnR6Sliw8BjAA--.3672S2 X-Coremail-Antispam: 1UD129KBjvJXoWxAF4rZF48trW3Zw1UZr4kCrg_yoWrGF18pF ZrKFWfJr4DXrW5AF48Cw4kJr1UZw1DXr98Ar18ZF4Sk3WxJrn8JF1DtryjqFW3KFZ0yF9r A34xXasxJF18uFJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUka1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8Jr0_Cr1UM28EF7xvwVC2 z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s0DM2AIxVAIcxkEcV Aq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1j 6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64 vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7MxAIw28IcxkI7VAKI48JMxAIw28IcVCjz48v 1sIEY20_GFWkJr1UJwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r 18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vI r41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Jr0_Gr 1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvE x4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUdHUDUUUUU= X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/1tbiAgMDAVZdtYkSWQAQsv Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org There are race conditions that may lead to null pointer dereferences in ax25_heartbeat_expiry(), ax25_t1timer_expiry(), ax25_t2timer_expiry(), ax25_t3timer_expiry() and ax25_idletimer_expiry(), when we use ax25_kill_by_device() to detach the ax25 device. One of the race conditions that cause null pointer dereferences can be shown as below: (Thread 1) | (Thread 2) ax25_connect() | ax25_std_establish_data_link() | ax25_start_t1timer() | mod_timer(&ax25->t1timer,..) | | ax25_kill_by_device() (wait a time) | ... | s->ax25_dev = NULL; //(1) ax25_t1timer_expiry() | ax25->ax25_dev->values[..] //(2)| ... ... | We set null to ax25_cb->ax25_dev in position (1) and dereference the null pointer in position (2). The corresponding fail log is shown below: =============================================================== BUG: kernel NULL pointer dereference, address: 0000000000000050 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc6-00794-g45690b7d0 RIP: 0010:ax25_t1timer_expiry+0x12/0x40 ... Call Trace: call_timer_fn+0x21/0x120 __run_timers.part.0+0x1ca/0x250 run_timer_softirq+0x2c/0x60 __do_softirq+0xef/0x2f3 irq_exit_rcu+0xb6/0x100 sysvec_apic_timer_interrupt+0xa2/0xd0 ... This patch uses ax25_disconnect() to delete timers before we set null to ax25_cb->ax25_dev in ax25_kill_by_device(). Function ax25_disconnect() will not return until all timers are stopped, because we have changed del_timer() to del_timer_sync(). What`s more, we could not use syscalls such as ax25_connect(), ax25_sendmsg() and so on to activate timers again unless we start the device, because we have set null to ax25_cb->ax25_dev. Signed-off-by: Duoming Zhou --- net/ax25/af_ax25.c | 4 ++-- net/ax25/ax25_timer.c | 16 +++++----------- 2 files changed, 7 insertions(+), 13 deletions(-) mode change 100644 => 100755 net/ax25/af_ax25.c mode change 100644 => 100755 net/ax25/ax25_timer.c -- 2.17.1 diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c old mode 100644 new mode 100755 index 6bd09718077..9a93ede3307 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -89,18 +89,18 @@ static void ax25_kill_by_device(struct net_device *dev) sk = s->sk; if (!sk) { spin_unlock_bh(&ax25_list_lock); - s->ax25_dev = NULL; ax25_disconnect(s, ENETUNREACH); + s->ax25_dev = NULL; spin_lock_bh(&ax25_list_lock); goto again; } sock_hold(sk); spin_unlock_bh(&ax25_list_lock); lock_sock(sk); + ax25_disconnect(s, ENETUNREACH); s->ax25_dev = NULL; dev_put_track(ax25_dev->dev, &ax25_dev->dev_tracker); ax25_dev_put(ax25_dev); - ax25_disconnect(s, ENETUNREACH); release_sock(sk); spin_lock_bh(&ax25_list_lock); sock_put(sk); diff --git a/net/ax25/ax25_timer.c b/net/ax25/ax25_timer.c old mode 100644 new mode 100755 index 85865ebfdfa..403d43fe1c6 --- a/net/ax25/ax25_timer.c +++ b/net/ax25/ax25_timer.c @@ -75,32 +75,26 @@ void ax25_start_idletimer(ax25_cb *ax25) else del_timer(&ax25->idletimer); } - void ax25_stop_heartbeat(ax25_cb *ax25) { - del_timer(&ax25->timer); + del_timer_sync(&ax25->timer); } - void ax25_stop_t1timer(ax25_cb *ax25) { - del_timer(&ax25->t1timer); + del_timer_sync(&ax25->t1timer); } - void ax25_stop_t2timer(ax25_cb *ax25) { - del_timer(&ax25->t2timer); + del_timer_sync(&ax25->t2timer); } - void ax25_stop_t3timer(ax25_cb *ax25) { - del_timer(&ax25->t3timer); + del_timer_sync(&ax25->t3timer); } - void ax25_stop_idletimer(ax25_cb *ax25) { - del_timer(&ax25->idletimer); + del_timer_sync(&ax25->idletimer); } - int ax25_t1timer_running(ax25_cb *ax25) { return timer_pending(&ax25->t1timer);