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=-10.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 306FDC433E0 for ; Tue, 23 Jun 2020 21:04:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F24E20702 for ; Tue, 23 Jun 2020 21:04:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592946240; bh=by/WlVmm+/tWieZc2nJ1fD/zD3sn1BSD5NO82MfLjhg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=wQM6/3gzng7tueXKRPKNL1OSE54VYTx0APRfUJsfx5ys7hcaP0Tu5VrrAEA0RdexF diwLiZET/PVRr1zqMHSHSBwZZY0ihYjd5fVXqdl0dOX+RVZ3XGRK5gCVGlL6AWNfIL cSwCtDLvzKG4+6pUSXKI8MvQIFYeGO9k+P0L1NfU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388912AbgFWVDt (ORCPT ); Tue, 23 Jun 2020 17:03:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:33800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391941AbgFWUiS (ORCPT ); Tue, 23 Jun 2020 16:38:18 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8881D2085B; Tue, 23 Jun 2020 20:38:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592944699; bh=by/WlVmm+/tWieZc2nJ1fD/zD3sn1BSD5NO82MfLjhg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ChV+7UGHJI7GXJ/kPL+KxaIL6Pk+xZIscxeH+xGqalc7YXuNRV8+koVbFaMg9LfHY Y5BawhqTe+TJhOWuR9GZcBaKKbD8+Qvv8yhpywGUmf3a2t6xI1UWSqg8exMxLktR8I /sbDRMyzuhOwYZb+JO2Abnc5Aj+KI02EcrkFE9nI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Raghavendra Rao Ananta , Sasha Levin Subject: [PATCH 4.19 063/206] tty: hvc: Fix data abort due to race in hvc_open Date: Tue, 23 Jun 2020 21:56:31 +0200 Message-Id: <20200623195320.062485366@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200623195316.864547658@linuxfoundation.org> References: <20200623195316.864547658@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 cdcc64ea2554f..f8e43a6faea9b 100644 --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -75,6 +75,8 @@ static LIST_HEAD(hvc_structs); */ static DEFINE_MUTEX(hvc_structs_mutex); +/* 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 @@ -346,16 +348,24 @@ 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); @@ -383,6 +393,8 @@ 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