From patchwork Fri Mar 18 00:54:05 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Duoming Zhou X-Patchwork-Id: 12784734 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 F0343C433EF for ; Fri, 18 Mar 2022 00:54:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231288AbiCRAzs (ORCPT ); Thu, 17 Mar 2022 20:55:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35112 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231268AbiCRAzp (ORCPT ); Thu, 17 Mar 2022 20:55:45 -0400 Received: from zju.edu.cn (spam.zju.edu.cn [61.164.42.155]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 93B7E186148; Thu, 17 Mar 2022 17:54:24 -0700 (PDT) Received: from ubuntu.localdomain (unknown [10.15.192.164]) by mail-app3 (Coremail) with SMTP id cC_KCgCn+ckw2DNijhwFAA--.6684S4; Fri, 18 Mar 2022 08:54:15 +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, eric.dumazet@gmail.com, dan.carpenter@oracle.com, Duoming Zhou Subject: [PATCH V6 2/2] ax25: Fix NULL pointer dereferences in ax25 timers Date: Fri, 18 Mar 2022 08:54:05 +0800 Message-Id: <95239e81883d3cd2b9e84c9e98d57b9b3fd52126.1647563511.git.duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 In-Reply-To: References: In-Reply-To: References: X-CM-TRANSID: cC_KCgCn+ckw2DNijhwFAA--.6684S4 X-Coremail-Antispam: 1UD129KBjvJXoWxGF45Cw45GF45Kry5Xw48Xrb_yoWrXr4xpF ZFgFWfJr4qqrW5Ar48Grs7JF4Uuw1qq3y5Ar18uF4S93ZrJrn8JFyDtFyUXFW3KFZxAF9r Aw18W39xZF18uaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvl1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8Jr0_Cr1UM28EF7xvwVC2 z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s0DM2AIxVAIcxkEcV Aq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1j 6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64 vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7M4IIrI8v6xkF7I0E8cxan2IY04v7MxAIw28I cxkI7VAKI48JMxAIw28IcVCjz48v1sIEY20_GFWkJr1UJwCFx2IqxVCFs4IE7xkEbVWUJV W8JwC20s026c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF 1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6x IIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvE x4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvj DU0xZFpf9x0JUdHUDUUUUU= X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/1tbiAgAMAVZdtYwINgAFsG Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org The previous commit 7ec02f5ac8a5 ("ax25: fix NPD bug in ax25_disconnect") move ax25_disconnect into lock_sock() in order to prevent NPD bugs. But 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 moves ax25_disconnect() before s->ax25_dev = NULL and uses del_timer_sync() to delete timers in ax25_disconnect(). If ax25_disconnect() is called by ax25_kill_by_device() or ax25->ax25_dev is NULL, the reason in ax25_disconnect() will be equal to ENETUNREACH, it will wait all timers to stop before we set null to s->ax25_dev in ax25_kill_by_device(). Fixes: 7ec02f5ac8a5 ("ax25: fix NPD bug in ax25_disconnect") Signed-off-by: Duoming Zhou --- Changes in V6: - Add Fixes tag. - Make commit message more clearer. net/ax25/af_ax25.c | 4 ++-- net/ax25/ax25_subr.c | 20 ++++++++++++++------ 2 files changed, 16 insertions(+), 8 deletions(-) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index cf8847cfc66..992b6e5d85d 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -89,20 +89,20 @@ 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; if (sk->sk_socket) { 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_subr.c b/net/ax25/ax25_subr.c index 15ab812c4fe..3a476e4f6cd 100644 --- a/net/ax25/ax25_subr.c +++ b/net/ax25/ax25_subr.c @@ -261,12 +261,20 @@ void ax25_disconnect(ax25_cb *ax25, int reason) { ax25_clear_queues(ax25); - if (!ax25->sk || !sock_flag(ax25->sk, SOCK_DESTROY)) - ax25_stop_heartbeat(ax25); - ax25_stop_t1timer(ax25); - ax25_stop_t2timer(ax25); - ax25_stop_t3timer(ax25); - ax25_stop_idletimer(ax25); + if (reason == ENETUNREACH) { + del_timer_sync(&ax25->timer); + del_timer_sync(&ax25->t1timer); + del_timer_sync(&ax25->t2timer); + del_timer_sync(&ax25->t3timer); + del_timer_sync(&ax25->idletimer); + } else { + if (!ax25->sk || !sock_flag(ax25->sk, SOCK_DESTROY)) + ax25_stop_heartbeat(ax25); + ax25_stop_t1timer(ax25); + ax25_stop_t2timer(ax25); + ax25_stop_t3timer(ax25); + ax25_stop_idletimer(ax25); + } ax25->state = AX25_STATE_0;