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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 9813CC433ED for ; Thu, 13 May 2021 10:25:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5CA4E613DF for ; Thu, 13 May 2021 10:25:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232675AbhEMK1A (ORCPT ); Thu, 13 May 2021 06:27:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:37672 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231572AbhEMK05 (ORCPT ); Thu, 13 May 2021 06:26:57 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CA2A661104; Thu, 13 May 2021 10:25:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620901547; bh=tGSbnJbV9mpjOtoS4fZRDhnpTdRQz/IXHDW4kTYpYAs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1I/jANeD3wLrWb04k8nKmsR8WskdmDEfQnDlB/qG+eYesSbsCu01am3HAH+SUqveR 7+y3F7VupADfNGsh3gkbc+FnaFq7W5XgtRmTEB2t2fychkG4zIpPchE/u1K4NCOF8I 5m1vFoYGXFebcrvbSvQbM6suE/okEvakNcJNX74Q= Date: Thu, 13 May 2021 12:25:44 +0200 From: Greg Kroah-Hartman To: Juergen Gross Cc: xen-devel@lists.xenproject.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Jiri Slaby Subject: Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value Message-ID: References: <20210513100302.22027-1-jgross@suse.com> <20210513100302.22027-9-jgross@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210513100302.22027-9-jgross@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 13, 2021 at 12:03:02PM +0200, Juergen Gross wrote: > Xen frontends shouldn't BUG() in case of illegal data received from > their backends. So replace the BUG_ON()s when reading illegal data from > the ring page with negative return values. > > Signed-off-by: Juergen Gross > --- > drivers/tty/hvc/hvc_xen.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c > index 92c9a476defc..30d7ffb1e04c 100644 > --- a/drivers/tty/hvc/hvc_xen.c > +++ b/drivers/tty/hvc/hvc_xen.c > @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons, > cons = intf->out_cons; > prod = intf->out_prod; > mb(); /* update queue values before going on */ > + > + if (WARN_ONCE((prod - cons) > sizeof(intf->out), > + "Illegal ring page indices")) > + return -EINVAL; How nice, you just rebooted on panic-on-warn systems :( > + > BUG_ON((prod - cons) > sizeof(intf->out)); Why keep this line? Please just fix this up properly, if userspace can trigger this, then both the WARN_ON() and BUG_ON() are not correct and need to be correctly handled. > > while ((sent < len) && ((prod - cons) < sizeof(intf->out))) > @@ -114,7 +119,10 @@ static int domU_write_console(uint32_t vtermno, const char *data, int len) > */ > while (len) { > int sent = __write_console(cons, data, len); > - > + > + if (sent < 0) > + return sent; > + > data += sent; > len -= sent; > > @@ -138,7 +146,10 @@ static int domU_read_console(uint32_t vtermno, char *buf, int len) > cons = intf->in_cons; > prod = intf->in_prod; > mb(); /* get pointers before reading ring */ > - BUG_ON((prod - cons) > sizeof(intf->in)); > + > + if (WARN_ONCE((prod - cons) > sizeof(intf->in), > + "Illegal ring page indices")) > + return -EINVAL; Same here, you still just paniced a machine :( thanks, greg k-h