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, URIBL_BLOCKED,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 B198BC4338F for ; Fri, 30 Jul 2021 15:13:34 +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 62EF760EFE for ; Fri, 30 Jul 2021 15:13:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 62EF760EFE 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.162594.298129 (Exim 4.92) (envelope-from ) id 1m9UCG-0007Tu-Nr; Fri, 30 Jul 2021 15:13:12 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 162594.298129; Fri, 30 Jul 2021 15:13:12 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1m9UCG-0007Ti-Kk; Fri, 30 Jul 2021 15:13:12 +0000 Received: by outflank-mailman (input) for mailman id 162594; Fri, 30 Jul 2021 15:13:11 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1m9UCF-0007Sr-HJ for xen-devel@lists.xenproject.org; Fri, 30 Jul 2021 15:13:11 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1m9UCD-0005IE-A1; Fri, 30 Jul 2021 15:13:09 +0000 Received: from 54-240-197-230.amazon.com ([54.240.197.230] 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 1m9UCD-0002Yl-1Z; Fri, 30 Jul 2021 15:13:09 +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=vhTbPeZFRrDcvsRQddWeO+kARioyLCWBCRabXZxJagc=; b=iuje+5YkzvURmjtFqMyCShT6zk KABClT//aU44daxnoHRaP0L+cqQJsf0YLf2zEEmeB95moryUsBJvWOspoMQkCBz9+q9PEipxgEb7A PNQYU40ArBccyzSMT2FsMwq5prKnQIW/y33S5LjmR3zI5V7GOKrP71Vrbo0B6/8Dx17A=; Subject: Re: [PATCH] tools/xenstored: Don't assume errno will not be overwritten in lu_arch() To: Juergen Gross , xen-devel@lists.xenproject.org Cc: Julien Grall , Ian Jackson , Wei Liu References: <20210729110647.25500-1-julien@xen.org> <3f3843c0-5766-b483-ce25-33fe2d4359ca@suse.com> From: Julien Grall Message-ID: Date: Fri, 30 Jul 2021 16:13:07 +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: <3f3843c0-5766-b483-ce25-33fe2d4359ca@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Hi Juergen, On 30/07/2021 09:40, Juergen Gross wrote: > On 29.07.21 17:23, Julien Grall wrote: >> >> >> 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. > > With setting errno to 0 before returning NULL in lu_binary() you can add > > Reviewed-by: Juergen Gross Thanks! I will commit it. Cheers, -- Julien Grall