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 X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4ED53C433E1 for ; Sun, 26 Jul 2020 05:29:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C408C204EA for ; Sun, 26 Jul 2020 05:29:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fudan.edu.cn header.i=@fudan.edu.cn header.b="TL3US7AT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726100AbgGZF2I (ORCPT ); Sun, 26 Jul 2020 01:28:08 -0400 Received: from mail.fudan.edu.cn ([202.120.224.10]:59497 "EHLO fudan.edu.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725747AbgGZF2I (ORCPT ); Sun, 26 Jul 2020 01:28:08 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fudan.edu.cn; s=dkim; h=Received:Date:From:To:Cc:Subject: Message-ID:MIME-Version:Content-Type:Content-Disposition; bh=i7I WTuXbIMWv0hCwBne9xxyRCcOriPNlgAzJOpZpCEo=; b=TL3US7ATed3gM8HMymo xL69dRRmyExiSXlTpMboHW1+GtUzi8iJxS6vBBf6Z9gWz6mxd8C7opbnqYCnXq3U wt5e7mPPGgCLrtfzs7xMmi4c8o6jnFhsIVIEp8iqJmQ6jGQ5BSgBE7Lvgzn1vZ0b L0pxyiEGCOe8KvNFqkGt0Tk8= Received: from xin-virtual-machine (unknown [114.252.69.253]) by app1 (Coremail) with SMTP id XAUFCgAnL_9kFB1fypU4Ag--.34557S3; Sun, 26 Jul 2020 13:28:04 +0800 (CST) Date: Sun, 26 Jul 2020 13:28:04 +0800 From: Xin Xiong To: Greg Kroah-Hartman , Jiri Slaby , linux-kernel@vger.kernel.org Cc: Xiyu Yang , Xin Tan , yuanxzhang@fudan.edu.cn, Xin Xiong Subject: [PATCH] tty: fix pid refcount leak in tty_signal_session_leader Message-ID: <20200726052804.GA51199@xin-virtual-machine> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-CM-TRANSID: XAUFCgAnL_9kFB1fypU4Ag--.34557S3 X-Coremail-Antispam: 1UD129KBjvJXoW7uF4fCry8tryfXFy5Zr4xJFb_yoW8Xw45pa 15J3yjyF98GF4UGrnrJ34FgFWFga4ftF97Gryqy34UAwsxAFyfKFy3Ka4jvF1qyrs5Zr1r uFW2vw13AF43ZFJanT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvq14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26F1j6w1UM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r4U JVWxJr1l84ACjcxK6I8E87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_Gc CE3s1lnxkEFVAIw20F6cxK64vIFxWle2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xv F2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_JrI_JrylYx0Ex4A2jsIE14v26r1j6r 4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvEwIxGrwACjI8F5VA0II8E6IAqYI8I648v 4I1lc2xSY4AK67AK6r4rMxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI 8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AK xVWUAVWUtwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI 8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_Zr0_Wr1UMIIF0xvEx4A2 jsIE14v26r1j6r4UMIIF0xvEx4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0x ZFpf9x0JUJb18UUUUU= X-CM-SenderInfo: arytiiqsuqiimz6i3vldqovvfxof0/ Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the loop, every time when p->signal->leader is true, the function tty_signal_session_leader() will invoke get_pid() and return a reference of tty->pgrp with increased refcount to the local variable tty_pgrp or return NULL if it fails. After finishing the loop, the function invokes put_pid() for only once, decreasing the refcount that tty_pgrp keeps. Refcount leaks may occur when the scenario that p->signal->leader is true happens more than once. In this assumption, if the above scenario happens n times in the loop, the function forgets to decrease the refcount for n-1 times, which causes refcount leaks. Fix the issue by decreasing the current refcount of the local variable tty_pgrp before assigning new objects to it. Signed-off-by: Xiyu Yang Signed-off-by: Xin Tan Signed-off-by: Xin Xiong --- drivers/tty/tty_jobctrl.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/tty/tty_jobctrl.c b/drivers/tty/tty_jobctrl.c index f8ed50a16848..9e6bf693ade1 100644 --- a/drivers/tty/tty_jobctrl.c +++ b/drivers/tty/tty_jobctrl.c @@ -212,6 +212,8 @@ int tty_signal_session_leader(struct tty_struct *tty, int exit_session) __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p); put_pid(p->signal->tty_old_pgrp); /* A noop */ spin_lock(&tty->ctrl_lock); + if (tty_pgrp) + put_pid(tty_pgrp); tty_pgrp = get_pid(tty->pgrp); if (tty->pgrp) p->signal->tty_old_pgrp = get_pid(tty->pgrp); -- 2.25.1