From patchwork Wed Jul 19 20:27:41 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 13319491 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 43456C001DC for ; Wed, 19 Jul 2023 20:37:58 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qMDv9-0005y6-AC; Wed, 19 Jul 2023 16:37:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qMDv7-0005w5-7H for qemu-devel@nongnu.org; Wed, 19 Jul 2023 16:37:13 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qMDv3-0001nO-Hb for qemu-devel@nongnu.org; Wed, 19 Jul 2023 16:37:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689799029; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=g/0in/JJ9xbwjl2UXjYiz+AmW55WbvctyTpKsyJT+Nk=; b=FdU93cRxE8Rk5FwX+8qOxR3RxxQFgw/604YL0AWsYkEB7Gftli5bYSTaH9UT1wzmpxCIYy hoaHxOPaslHZZ1PnnJ1QXhQU+54FBlYENU58y+Bj6HbFqrrSMnqU1s+zfi8wAocaz/Z9y+ BHRgoTHb6Fv9fNMt9eE+PvIFJP/6mmA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-344-4EYrFRauMKmZRHXBBT_hEg-1; Wed, 19 Jul 2023 16:37:05 -0400 X-MC-Unique: 4EYrFRauMKmZRHXBBT_hEg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E6212810BB2; Wed, 19 Jul 2023 20:37:04 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.192]) by smtp.corp.redhat.com (Postfix) with ESMTP id 80D044CD0F8; Wed, 19 Jul 2023 20:37:04 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: "Denis V. Lunev" , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org (open list:Network Block Dev...) Subject: [PULL 04/14] qemu-nbd: properly report error on error in dup2() after qemu_daemon() Date: Wed, 19 Jul 2023 15:27:41 -0500 Message-ID: <20230719202736.2675295-20-eblake@redhat.com> In-Reply-To: <20230719202736.2675295-16-eblake@redhat.com> References: <20230719202736.2675295-16-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: "Denis V. Lunev" We are trying to temporarily redirect stderr of daemonized process to a pipe to report a error and get failed. In that case we could not use error_report() helper, but should write the message directly into the problematic pipe. Signed-off-by: Denis V. Lunev CC: Eric Blake CC: Vladimir Sementsov-Ogievskiy Message-ID: <20230717145544.194786-4-den@openvz.org> Reviewed-by: Eric Blake [eblake: rearrange patch series, fix typo] Signed-off-by: Eric Blake --- qemu-nbd.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/qemu-nbd.c b/qemu-nbd.c index 5a8ae1f7472..f27613cb572 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -940,7 +940,20 @@ int main(int argc, char **argv) saved_errno = errno; /* dup2 will overwrite error below */ /* Temporarily redirect stderr to the parent's pipe... */ - dup2(stderr_fd[1], STDERR_FILENO); + if (dup2(stderr_fd[1], STDERR_FILENO) < 0) { + char str[256]; + snprintf(str, sizeof(str), + "%s: Failed to link stderr to the pipe: %s\n", + g_get_prgname(), strerror(errno)); + /* + * We are unable to use error_report() here as we need to get + * stderr pointed to the parent's pipe. Write to that pipe + * manually. + */ + ret = write(stderr_fd[1], str, strlen(str)); + exit(EXIT_FAILURE); + } + if (ret < 0) { error_report("Failed to daemonize: %s", strerror(saved_errno)); exit(EXIT_FAILURE);