From patchwork Tue Jun 9 17:45:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 224657 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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, 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 815B3C433E0 for ; Tue, 9 Jun 2020 18:01:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 62653206D5 for ; Tue, 9 Jun 2020 18:01:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591725676; bh=7H0o9iPkpfeRrO+kK8fHciPXul+ErU2mXc1tBvSlrxs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=jgoUMPxyvODIOj0So4gWHyv4LM78mTbEz3yu1aYO035p8eoEp94Am/0IPuyjvtNyS 9EcVPP3aKTOehN59udK5DsNEJjFPrjflowp1l2XrUu0pgkxZv4GAoUtvYvu+xVxUmg y3qUIxzKIJiP3dQfy6VDfGOnv9nOYjJDAys9JjFI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387470AbgFISAt (ORCPT ); Tue, 9 Jun 2020 14:00:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:45756 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733071AbgFIRyN (ORCPT ); Tue, 9 Jun 2020 13:54:13 -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 833AF20801; Tue, 9 Jun 2020 17:54:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591725253; bh=7H0o9iPkpfeRrO+kK8fHciPXul+ErU2mXc1tBvSlrxs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fuNdg4krJBg/3222C9pFqowxCLjvqaD2qXsUallGff7InQVImI6fWJd0XPKX4OI0w Fq+45pSCtBGtFsGbzxKMzDFmnI7gJSJ1RXA0g/fzY6mh33MSNjNTxui7oY4PFu99y/ AMY0oodi/PLpBdWpw2mujDaqjTu1TodvBdGBj7Vg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiri Slaby , Raghavendra Subject: [PATCH 5.6 31/41] tty: hvc_console, fix crashes on parallel open/close Date: Tue, 9 Jun 2020 19:45:33 +0200 Message-Id: <20200609174115.064905891@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200609174112.129412236@linuxfoundation.org> References: <20200609174112.129412236@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jiri Slaby commit 24eb2377f977fe06d84fca558f891f95bc28a449 upstream. hvc_open sets tty->driver_data to NULL when open fails at some point. Typically, the failure happens in hp->ops->notifier_add(). If there is a racing process which tries to open such mangled tty, which was not closed yet, the process will crash in hvc_open as tty->driver_data is NULL. All this happens because close wants to know whether open failed or not. But ->open should not NULL this and other tty fields for ->close to be happy. ->open should call tty_port_set_initialized(true) and close should check by tty_port_initialized() instead. So do this properly in this driver. So this patch removes these from ->open: * tty_port_tty_set(&hp->port, NULL). This happens on last close. * tty->driver_data = NULL. Dtto. * tty_port_put(&hp->port). This happens in shutdown and until now, this must have been causing a reference underflow, if I am not missing something. Signed-off-by: Jiri Slaby Cc: stable Reported-and-tested-by: Raghavendra Link: https://lore.kernel.org/r/20200526145632.13879-1-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman --- drivers/tty/hvc/hvc_console.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -371,15 +371,14 @@ static int hvc_open(struct tty_struct *t * tty fields and return the kref reference. */ if (rc) { - tty_port_tty_set(&hp->port, NULL); - tty->driver_data = NULL; - tty_port_put(&hp->port); printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc); - } else + } else { /* We are ready... raise DTR/RTS */ if (C_BAUD(tty)) if (hp->ops->dtr_rts) hp->ops->dtr_rts(hp, 1); + tty_port_set_initialized(&hp->port, true); + } /* Force wakeup of the polling thread */ hvc_kick(); @@ -389,22 +388,12 @@ static int hvc_open(struct tty_struct *t static void hvc_close(struct tty_struct *tty, struct file * filp) { - struct hvc_struct *hp; + struct hvc_struct *hp = tty->driver_data; unsigned long flags; if (tty_hung_up_p(filp)) return; - /* - * No driver_data means that this close was issued after a failed - * hvc_open by the tty layer's release_dev() function and we can just - * exit cleanly because the kref reference wasn't made. - */ - if (!tty->driver_data) - return; - - hp = tty->driver_data; - spin_lock_irqsave(&hp->port.lock, flags); if (--hp->port.count == 0) { @@ -412,6 +401,9 @@ static void hvc_close(struct tty_struct /* We are done with the tty pointer now. */ tty_port_tty_set(&hp->port, NULL); + if (!tty_port_initialized(&hp->port)) + return; + if (C_HUPCL(tty)) if (hp->ops->dtr_rts) hp->ops->dtr_rts(hp, 0); @@ -428,6 +420,7 @@ static void hvc_close(struct tty_struct * waking periodically to check chars_in_buffer(). */ tty_wait_until_sent(tty, HVC_CLOSE_WAIT); + tty_port_set_initialized(&hp->port, false); } else { if (hp->port.count < 0) printk(KERN_ERR "hvc_close %X: oops, count is %d\n",