From mboxrd@z Thu Jan 1 00:00:00 1970 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 59707C001B0 for ; Fri, 11 Aug 2023 03:12:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231214AbjHKDMP (ORCPT ); Thu, 10 Aug 2023 23:12:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60136 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229600AbjHKDMO (ORCPT ); Thu, 10 Aug 2023 23:12:14 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 06C472D65 for ; Thu, 10 Aug 2023 20:12:12 -0700 (PDT) Received: from kwepemm600014.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4RMTJm5g0gzCrXd; Fri, 11 Aug 2023 11:08:40 +0800 (CST) Received: from ubuntu1804.huawei.com (10.67.175.28) by kwepemm600014.china.huawei.com (7.193.23.54) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Fri, 11 Aug 2023 11:12:09 +0800 From: Yi Yang To: , , , CC: , Subject: [PATCH] tty: n_gsm: fix the UAF caused by race condition in gsm_cleanup_mux Date: Fri, 11 Aug 2023 11:11:21 +0800 Message-ID: <20230811031121.153237-1-yiyang13@huawei.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.67.175.28] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemm600014.china.huawei.com (7.193.23.54) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org In commit 9b9c8195f3f0 ("tty: n_gsm: fix UAF in gsm_cleanup_mux"), the UAF problem is not completely fixed. There is a race condition in gsm_cleanup_mux(), which caused this UAF. The UAF problem is triggered by the following race: task[5046] task[5054] ----------------------- ----------------------- gsm_cleanup_mux(); dlci = gsm->dlci[0]; mutex_lock(&gsm->mutex); gsm_cleanup_mux(); dlci = gsm->dlci[0]; //Didn't take the lock gsm_dlci_release(gsm->dlci[i]); gsm->dlci[i] = NULL; mutex_unlock(&gsm->mutex); mutex_lock(&gsm->mutex); dlci->dead = true; //UAF Fix it by assigning values after mutex_lock(). Link: https://syzkaller.appspot.com/text?tag=CrashReport&x=176188b5a80000 Fixes: 9b9c8195f3f0 ("tty: n_gsm: fix UAF in gsm_cleanup_mux") Fixes: aa371e96f05d ("tty: n_gsm: fix restart handling via CLD command") Signed-off-by: Yi Yang Co-developed-by: Qiumiao Zhang Signed-off-by: Qiumiao Zhang --- drivers/tty/n_gsm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index c7a787f10a9c..b32d91ccddda 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -3042,12 +3042,13 @@ static void gsm_error(struct gsm_mux *gsm) static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc) { int i; - struct gsm_dlci *dlci = gsm->dlci[0]; + struct gsm_dlci *dlci; struct gsm_msg *txq, *ntxq; gsm->dead = true; mutex_lock(&gsm->mutex); + dlci = gsm->dlci[0]; if (dlci) { if (disc && dlci->state != DLCI_CLOSED) { gsm_dlci_begin_close(dlci); -- 2.17.1