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=-17.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 B1186C432BE for ; Thu, 29 Jul 2021 15:23:21 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 7BFAF60F43 for ; Thu, 29 Jul 2021 15:23:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7BFAF60F43 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.161984.297211 (Exim 4.92) (envelope-from ) id 1m97sK-0003va-8a; Thu, 29 Jul 2021 15:23:08 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 161984.297211; Thu, 29 Jul 2021 15:23:08 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1m97sK-0003vT-4V; Thu, 29 Jul 2021 15:23:08 +0000 Received: by outflank-mailman (input) for mailman id 161984; Thu, 29 Jul 2021 15:23:07 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1m97sJ-0003vN-00 for xen-devel@lists.xenproject.org; Thu, 29 Jul 2021 15:23:07 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1m97sF-0000Ke-Ny; Thu, 29 Jul 2021 15:23:03 +0000 Received: from 54-240-197-232.amazon.com ([54.240.197.232] helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1m97sF-00060j-Hd; Thu, 29 Jul 2021 15:23:03 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=4oYLqXu9qM5umKlMiN8kk9cvkLylv/S7RA/yT8wVoaw=; b=bbx0RS4zEDotLt8I7cGHPrP7+7 DBYedWuJW9gAj88vz0hu+CbZWv6ZXnqtJZjJa7MDythmrM1UmvC6MWbIHQCW4CIVVDKC1cm7jme2p wFdzMXxTdLWMruv54F/VLfCmhjLzWUcow28VH1zXW385obUuJHJDg9lbOmGVQUm3Nf0s=; Subject: Re: [PATCH] tools/xenstored: Don't assume errno will not be overwritten in lu_arch() To: xen-devel@lists.xenproject.org Cc: Julien Grall , Ian Jackson , Wei Liu , Juergen Gross References: <20210729110647.25500-1-julien@xen.org> From: Julien Grall Message-ID: Date: Thu, 29 Jul 2021 16:23:01 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210729110647.25500-1-julien@xen.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit On 29/07/2021 12:06, Julien Grall wrote: > From: Julien Grall > > At the moment, do_control_lu() will set errno to 0 before calling > lu_arch() and then check errno. The expectation is nothing in lu_arch() > will change the value unless there is an error. > > However, per errno(3), a function that succeeds is allowed to change > errno. In fact, syslog() will overwrite errno if the logs are rotated > at the time it is called. > > To prevent any further issue, errno is now always set before > returning NULL. > > Additionally, errno is only checked when returning NULL so the client > can see the error message if there is any. > > Reported-by: Michael Kurth > Signed-off-by: Julien Grall > --- > tools/xenstore/xenstored_control.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/tools/xenstore/xenstored_control.c b/tools/xenstore/xenstored_control.c > index 6b68b79faac7..6fcb42095b59 100644 > --- a/tools/xenstore/xenstored_control.c > +++ b/tools/xenstore/xenstored_control.c > @@ -324,6 +324,7 @@ static const char *lu_binary_alloc(const void *ctx, struct connection *conn, > lu_status->kernel_size = size; > lu_status->kernel_off = 0; > > + errno = 0; > return NULL; > } > > @@ -339,6 +340,7 @@ static const char *lu_binary_save(const void *ctx, struct connection *conn, > memcpy(lu_status->kernel + lu_status->kernel_off, data, size); > lu_status->kernel_off += size; > > + errno = 0; > return NULL; > } > I forgot to update lu_binary(). I will respin the patch once I get some feedback. Cheers, > @@ -798,9 +800,8 @@ static int do_control_lu(void *ctx, struct connection *conn, > if (!ret) > return errno; > } else { > - errno = 0; > ret = lu_arch(ctx, conn, vec, num); > - if (errno) > + if (!ret && errno) > return errno; > } > > -- Julien Grall