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 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 E7F12EB64DC for ; Mon, 17 Jul 2023 14:57:36 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qLPe1-0002Tf-3O; Mon, 17 Jul 2023 10:56:13 -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 1qLPdh-0002NZ-J5; Mon, 17 Jul 2023 10:55:53 -0400 Received: from relay.virtuozzo.com ([130.117.225.111]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qLPdd-0003kY-WC; Mon, 17 Jul 2023 10:55:53 -0400 Received: from ch-vpn.virtuozzo.com ([130.117.225.6] helo=iris.sw.ru) by relay.virtuozzo.com with esmtp (Exim 4.96) (envelope-from ) id 1qLPc1-00HTc0-2U; Mon, 17 Jul 2023 16:55:39 +0200 From: "Denis V. Lunev" To: qemu-block@nongnu.org, qemu-devel@nongnu.org Cc: den@openvz.org, Eric Blake , Vladimir Sementsov-Ogievskiy Subject: [PATCH 3/5] qemu-nbd: properly report error on error in dup2() after qemu_daemon() Date: Mon, 17 Jul 2023 16:55:42 +0200 Message-Id: <20230717145544.194786-4-den@openvz.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230717145544.194786-1-den@openvz.org> References: <20230717145544.194786-1-den@openvz.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=130.117.225.111; envelope-from=den@openvz.org; helo=relay.virtuozzo.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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 We are trying to temporary 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 --- qemu-nbd.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/qemu-nbd.c b/qemu-nbd.c index 186ce9474c..4450cc826b 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -937,7 +937,20 @@ int main(int argc, char **argv) ret = qemu_daemon(1, 0); /* 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(errno)); exit(EXIT_FAILURE); -- 2.34.1