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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_GIT 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 4FE38C28CC1 for ; Sat, 1 Jun 2019 13:27:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2762F26C02 for ; Sat, 1 Jun 2019 13:27:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559395653; bh=VBtP+46+0ikRfN2VCn1+6UuYyC/LkPlmOox4Ox07x1o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ETPUYpZXOWQBDWgOA80/XJj2WMTIKgC4QmDgYAn3BcNbOpyMn9e+twNjsoFPPZ6Dv kWOKBo6+Ktfp88WnGTTTlUxvaQHIi21MqAWowB9Gzwi6nLbVggczpgyJ8Hto6zTRQA qWLaiOzhiQEzmZ2vVY/dDkMaXrU8hocmWky/mN94= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729968AbfFAN1b (ORCPT ); Sat, 1 Jun 2019 09:27:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:59204 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729952AbfFAN13 (ORCPT ); Sat, 1 Jun 2019 09:27:29 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2BDB524EEF; Sat, 1 Jun 2019 13:27:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559395648; bh=VBtP+46+0ikRfN2VCn1+6UuYyC/LkPlmOox4Ox07x1o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DKONGtQ1yF0m9jgJyYND6Wd/BJsfQcCyg4PTN4qGCnTRE35dBHks6w9pR3AHTTaZ3 HgGQGsbfbB2KKTOErbwIXSZDoW5onamE8Ygjys3/X7+2d7qPG7OyhP5C1Apk92w4f+ uM5YdgQWcXHG2ksBIs5q2MNebv/KdsXY37E5hKr4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sahara , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 4.4 50/56] tty: pty: Fix race condition between release_one_tty and pty_write Date: Sat, 1 Jun 2019 09:25:54 -0400 Message-Id: <20190601132600.27427-50-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190601132600.27427-1-sashal@kernel.org> References: <20190601132600.27427-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sahara [ Upstream commit b9ca5f8560af244489b4a1bc1ae88b341f24bc95 ] Especially when a linked tty is used such as pty, the linked tty port's buf works have not been cancelled while master tty port's buf work has been cancelled. Since release_one_tty and flush_to_ldisc run in workqueue threads separately, when pty_cleanup happens and link tty port is freed, flush_to_ldisc tries to access freed port and port->itty, eventually it causes a panic. This patch utilizes the magic value with holding the tty_mutex to check if the tty->link is valid. Fixes: 2b022ab7542d ("pty: cancel pty slave port buf's work in tty_release") Signed-off-by: Sahara Cc: stable Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/pty.c | 7 +++++++ drivers/tty/tty_io.c | 3 +++ 2 files changed, 10 insertions(+) diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c index c8a2e5b0eff76..0e10600f3884d 100644 --- a/drivers/tty/pty.c +++ b/drivers/tty/pty.c @@ -111,6 +111,12 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c) if (tty->stopped) return 0; + mutex_lock(&tty_mutex); + if (to->magic != TTY_MAGIC) { + mutex_unlock(&tty_mutex); + return -EIO; + } + if (c > 0) { spin_lock_irqsave(&to->port->lock, flags); /* Stuff the data into the input queue of the other end */ @@ -120,6 +126,7 @@ static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c) tty_flip_buffer_push(to->port); spin_unlock_irqrestore(&to->port->lock, flags); } + mutex_unlock(&tty_mutex); return c; } diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index b7effcfee91d8..acaf244859039 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1639,10 +1639,13 @@ static void release_one_tty(struct work_struct *work) struct tty_driver *driver = tty->driver; struct module *owner = driver->owner; + mutex_lock(&tty_mutex); if (tty->ops->cleanup) tty->ops->cleanup(tty); tty->magic = 0; + mutex_unlock(&tty_mutex); + tty_driver_kref_put(driver); module_put(owner); -- 2.20.1