From patchwork Tue Apr 26 08:21:31 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 567995 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 5D8D0C433F5 for ; Tue, 26 Apr 2022 08:33:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345146AbiDZIgm (ORCPT ); Tue, 26 Apr 2022 04:36:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345706AbiDZIfE (ORCPT ); Tue, 26 Apr 2022 04:35:04 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D71A27B55A; Tue, 26 Apr 2022 01:28:10 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 72A666185D; Tue, 26 Apr 2022 08:28:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7CF7DC385A0; Tue, 26 Apr 2022 08:28:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650961689; bh=jbbmtksSfJI1eUfbKZ/USS771t/kdVO6YQFAeSBx6J4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JgjZgQXdCO49PZ5PYovupyvpAEur4IePqO9QNmgASRfv65YkIB1Ad7wSEijrk7s6o xBt34MRpV1DvCnhlM8jncrllhFbyzlwvgorvrJTpwW47lBlObc04olD3PGxlgJq7c4 9XKOPok6lNeDKvS1IWQ2UE2tOtaI8k+dmWnefVb8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Duoming Zhou , "David S. Miller" , Ovidiu Panait Subject: [PATCH 4.19 51/53] ax25: Fix NULL pointer dereferences in ax25 timers Date: Tue, 26 Apr 2022 10:21:31 +0200 Message-Id: <20220426081737.149560487@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220426081735.651926456@linuxfoundation.org> References: <20220426081735.651926456@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Duoming Zhou commit fc6d01ff9ef03b66d4a3a23b46fc3c3d8cf92009 upstream. 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 Signed-off-by: David S. Miller [OP: backport to 4.19: adjust context] Signed-off-by: Ovidiu Panait Signed-off-by: Greg Kroah-Hartman --- net/ax25/af_ax25.c | 4 ++-- net/ax25/ax25_subr.c | 20 ++++++++++++++------ 2 files changed, 16 insertions(+), 8 deletions(-) --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -92,20 +92,20 @@ again: 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(ax25_dev->dev); ax25_dev_put(ax25_dev); } - ax25_disconnect(s, ENETUNREACH); release_sock(sk); spin_lock_bh(&ax25_list_lock); sock_put(sk); --- a/net/ax25/ax25_subr.c +++ b/net/ax25/ax25_subr.c @@ -264,12 +264,20 @@ void ax25_disconnect(ax25_cb *ax25, int { 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;