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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 BB848C433DF for ; Thu, 18 Jun 2020 01:35:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B72120776 for ; Thu, 18 Jun 2020 01:35:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592444127; bh=th7X71BqQW2FaajUKXQspd9Aq58319XeV8XowdC2hjw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xqVokXGmJJ6Mc0UfccsY3n8xkVxurrsTlHQ7a45+kc6fHGIOMtqjkNNlNCOexlx6Y dJyRl0KjijutsXt/3Nt5EEWS4oqAwXo6ITW6G51I2nsh19YY+N9IAqCss6pMWFtS9H lrbdg+21wEc3xgzDUcDZPlqgjw2fFj+8DSb65lEs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732802AbgFRBbi (ORCPT ); Wed, 17 Jun 2020 21:31:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:38164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732225AbgFRB3E (ORCPT ); Wed, 17 Jun 2020 21:29:04 -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 2AB8022208; Thu, 18 Jun 2020 01:29:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592443743; bh=th7X71BqQW2FaajUKXQspd9Aq58319XeV8XowdC2hjw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sAJhjHOg+UnwxEi2J7dj8/yiiD3Wg0vHyaRMneV9b99yQ4I9kOhtnTGBAPK+RNOr+ 9nrecXrWGeQizWE6+EHQmCgA72VLf8iS5HobHBGV/MPvM9SirB2aQ/YxUVDP32WEhs W9PCCAj5Xz96PrIO/DBQrt6Uty24llTeMejmVT/0= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Raghavendra Rao Ananta , Greg Kroah-Hartman , Sasha Levin , linuxppc-dev@lists.ozlabs.org Subject: [PATCH AUTOSEL 4.9 33/80] tty: hvc: Fix data abort due to race in hvc_open Date: Wed, 17 Jun 2020 21:27:32 -0400 Message-Id: <20200618012819.609778-33-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200618012819.609778-1-sashal@kernel.org> References: <20200618012819.609778-1-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: Raghavendra Rao Ananta [ Upstream commit e2bd1dcbe1aa34ff5570b3427c530e4332ecf0fe ] Potentially, hvc_open() can be called in parallel when two tasks calls open() on /dev/hvcX. In such a scenario, if the hp->ops->notifier_add() callback in the function fails, where it sets the tty->driver_data to NULL, the parallel hvc_open() can see this NULL and cause a memory abort. Hence, serialize hvc_open and check if tty->private_data is NULL before proceeding ahead. The issue can be easily reproduced by launching two tasks simultaneously that does nothing but open() and close() on /dev/hvcX. For example: $ ./simple_open_close /dev/hvc0 & ./simple_open_close /dev/hvc0 & Signed-off-by: Raghavendra Rao Ananta Link: https://lore.kernel.org/r/20200428032601.22127-1-rananta@codeaurora.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/hvc/hvc_console.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c index 985f49a65906..35d591287734 100644 --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -89,6 +89,8 @@ static LIST_HEAD(hvc_structs); */ static DEFINE_SPINLOCK(hvc_structs_lock); +/* Mutex to serialize hvc_open */ +static DEFINE_MUTEX(hvc_open_mutex); /* * This value is used to assign a tty->index value to a hvc_struct based * upon order of exposure via hvc_probe(), when we can not match it to @@ -333,16 +335,24 @@ static int hvc_install(struct tty_driver *driver, struct tty_struct *tty) */ static int hvc_open(struct tty_struct *tty, struct file * filp) { - struct hvc_struct *hp = tty->driver_data; + struct hvc_struct *hp; unsigned long flags; int rc = 0; + mutex_lock(&hvc_open_mutex); + + hp = tty->driver_data; + if (!hp) { + rc = -EIO; + goto out; + } + spin_lock_irqsave(&hp->port.lock, flags); /* Check and then increment for fast path open. */ if (hp->port.count++ > 0) { spin_unlock_irqrestore(&hp->port.lock, flags); hvc_kick(); - return 0; + goto out; } /* else count == 0 */ spin_unlock_irqrestore(&hp->port.lock, flags); @@ -370,6 +380,8 @@ static int hvc_open(struct tty_struct *tty, struct file * filp) /* Force wakeup of the polling thread */ hvc_kick(); +out: + mutex_unlock(&hvc_open_mutex); return rc; } -- 2.25.1