From patchwork Thu Apr 6 11:20:41 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bin Meng X-Patchwork-Id: 13203182 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 B6BABC76196 for ; Thu, 6 Apr 2023 11:21:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pkNg0-0004h6-Mx; Thu, 06 Apr 2023 07:21:12 -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 1pkNfv-0004gY-AG for qemu-devel@nongnu.org; Thu, 06 Apr 2023 07:21:07 -0400 Received: from bg4.exmail.qq.com ([43.155.65.254]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pkNfs-0007tI-Iu for qemu-devel@nongnu.org; Thu, 06 Apr 2023 07:21:06 -0400 X-QQ-mid: bizesmtp68t1680780043txb4wgzv Received: from ubuntu.. ( [111.196.129.125]) by bizesmtp.qq.com (ESMTP) with id ; Thu, 06 Apr 2023 19:20:41 +0800 (CST) X-QQ-SSF: 01200000000000D0F000000A0000000 X-QQ-FEAT: y8yRZXWSBv8XDu98VW9eqYuJ+tCFttGT70X3gcnHq7waThDDGlr+vyKCoPgZd q+JlQxiXi5c8vzPITXLE9SaNhfnvRWNjXf+DT8Fyi2/nijsp0C7rpW/m24+36WoPJ4XFrsZ PfSc3Oj1X7Nx8CZsHaO1dk133Fd25Hf0Sp0Zoy8vPeFj/fOLkv6IpYJRgYGyxNMlMQfOiDp 2WhbboVAdPyEO+rzBZyWfM4CiKVaiS5Ydey5zTagtRgJwOZXYy96LaRvGdUZwVBBrmb4hmT MHLnqxMrHiZRrlQZOMQKR9AJTYl3Aqfch/mrVDeNG5vQnanSXAtgCmJSVrMPdTA2H/mQmN4 emyBGpwctmqrU9yJik= X-QQ-GoodBg: 0 X-BIZMAIL-ID: 1490128918408474589 From: Bin Meng To: Jason Wang , qemu-devel@nongnu.org Cc: Zhangjin Wu Subject: [PATCH] net: tap: Drop the close of fds for child process Date: Thu, 6 Apr 2023 19:20:41 +0800 Message-Id: <20230406112041.798585-1-bmeng@tinylab.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-QQ-SENDSIZE: 520 Feedback-ID: bizesmtp:tinylab.org:qybglogicsvr:qybglogicsvr3 Received-SPF: pass client-ip=43.155.65.254; envelope-from=bmeng@tinylab.org; helo=bg4.exmail.qq.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, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 Current codes using a brute-force traversal of all file descriptors do not scale on a system where the maximum number of file descriptors are set to a very large value (e.g.: in a Docker container of Manjaro distribution it is set to 1073741816). QEMU just looks freezed during start-up. The close-on-exec flag was introduced since a faily old Linux kernel (2.6.23). With recent newer kernels that QEMU supports, we don't need to manually close the fds for child process as the proper O_CLOEXEC flag should have been set properly on files that we don't want child process to see. Reported-by: Zhangjin Wu Signed-off-by: Bin Meng --- net/tap.c | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/net/tap.c b/net/tap.c index 1bf085d422..49e1915484 100644 --- a/net/tap.c +++ b/net/tap.c @@ -446,13 +446,6 @@ static void launch_script(const char *setup_script, const char *ifname, return; } if (pid == 0) { - int open_max = sysconf(_SC_OPEN_MAX), i; - - for (i = 3; i < open_max; i++) { - if (i != fd) { - close(i); - } - } parg = args; *parg++ = (char *)setup_script; *parg++ = (char *)ifname; @@ -536,17 +529,10 @@ static int net_bridge_run_helper(const char *helper, const char *bridge, return -1; } if (pid == 0) { - int open_max = sysconf(_SC_OPEN_MAX), i; char *fd_buf = NULL; char *br_buf = NULL; char *helper_cmd = NULL; - for (i = 3; i < open_max; i++) { - if (i != sv[1]) { - close(i); - } - } - fd_buf = g_strdup_printf("%s%d", "--fd=", sv[1]); if (strrchr(helper, ' ') || strrchr(helper, '\t')) {