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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 97F04C433DF for ; Wed, 20 May 2020 09:41:44 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 07F712075F for ; Wed, 20 May 2020 09:41:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07F712075F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49Rnnx2WKXzDqW6 for ; Wed, 20 May 2020 19:41:41 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=suse.cz (client-ip=195.135.220.15; helo=mx2.suse.de; envelope-from=jslaby@suse.cz; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=suse.cz Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 49Rnkq0BN9zDqVF for ; Wed, 20 May 2020 19:38:58 +1000 (AEST) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id EFB83AC61; Wed, 20 May 2020 09:38:57 +0000 (UTC) Subject: Re: [PATCH] tty: hvc: Fix data abort due to race in hvc_open To: rananta@codeaurora.org, Greg KH References: <20200428032601.22127-1-rananta@codeaurora.org> <20200506094851.GA2787548@kroah.com> <98bbe7afabf48d8e8fe839fdc9e836a5@codeaurora.org> <20200510064819.GB3400311@kroah.com> <77d889be4e0cb0e6e30f96199e2d843d@codeaurora.org> <20200511073913.GA1347819@kroah.com> <0f7791f5-0a53-59f6-7277-247a789f30c2@suse.cz> <20200512082551.GA3526567@kroah.com> <417b1d320bda37410788430979dd708d@codeaurora.org> <20200513070403.GB764901@kroah.com> <0ab0b49f19b824ac1c4db4c4937ed388@codeaurora.org> From: Jiri Slaby Autocrypt: addr=jslaby@suse.cz; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <0ab0b49f19b824ac1c4db4c4937ed388@codeaurora.org> Content-Type: multipart/mixed; boundary="------------37BE8DE752E63BA265E3EAA7" Content-Language: en-US X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: andrew@daynix.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" This is a multi-part message in MIME format. --------------37BE8DE752E63BA265E3EAA7 Content-Type: text/plain; charset=iso-8859-2 Content-Transfer-Encoding: 8bit On 15. 05. 20, 1:22, rananta@codeaurora.org wrote: > On 2020-05-13 00:04, Greg KH wrote: >> On Tue, May 12, 2020 at 02:39:50PM -0700, rananta@codeaurora.org wrote: >>> On 2020-05-12 01:25, Greg KH wrote: >>> > On Tue, May 12, 2020 at 09:22:15AM +0200, Jiri Slaby wrote: >>> > > commit bdb498c20040616e94b05c31a0ceb3e134b7e829 >>> > > Author: Jiri Slaby >>> > > Date:   Tue Aug 7 21:48:04 2012 +0200 >>> > > >>> > >     TTY: hvc_console, add tty install >>> > > >>> > > added hvc_install but did not move 'tty->driver_data = NULL;' from >>> > > hvc_open's fail path to hvc_cleanup. >>> > > >>> > > IOW hvc_open now NULLs tty->driver_data even for another task which >>> > > opened the tty earlier. The same holds for >>> > > "tty_port_tty_set(&hp->port, >>> > > NULL);" there. And actually "tty_port_put(&hp->port);" is also >>> > > incorrect >>> > > for the 2nd task opening the tty. >>> > > ... > These are the traces you get when the issue happens: > [  154.212291] hvc_install called for pid: 666 > [  154.216705] hvc_open called for pid: 666 > [  154.233657] hvc_open: request_irq failed with rc -22. > [  154.238934] hvc_open called for pid: 678 > [  154.243012] Unable to handle kernel NULL pointer dereference at > virtual address 00000000000000c4 > # hvc_install isn't called for pid: 678 as the file wasn't closed yet. Nice. Does the attached help? I wonder how comes the tty_port_put in hvc_open does not cause a UAF? I would say hvc_open fails, tty_port_put is called. It decrements the reference taken in hvc_install. So far so good. Now, this should happen IMO: tty_open -> hvc_open (fails) -> tty_port_put -> tty_release -> tty_release_struct -> tty_kref_put -> queue_release_one_tty SCHEDULED WORKQUEUE release_one_tty -> hvc_cleanup -> tty_port_put (should die terrible death now) What am I missing? thanks, -- js suse labs --------------37BE8DE752E63BA265E3EAA7 Content-Type: text/x-patch; charset=UTF-8; name="0001-hvc_console-fix-open.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-hvc_console-fix-open.patch" >From d891cdfcbd3b41eb23ddfc8d9e6cbe038ff8fb72 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Wed, 20 May 2020 11:29:25 +0200 Subject: [PATCH] hvc_console: fix open Signed-off-by: Jiri Slaby --- drivers/tty/hvc/hvc_console.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c index 436cc51c92c3..cdcc64ea2554 100644 --- 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 *tty, struct file * filp) * 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 *tty, struct file * filp) 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 *tty, struct file * filp) /* 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 *tty, struct file * filp) * 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", -- 2.26.2 --------------37BE8DE752E63BA265E3EAA7--