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=-9.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 A5E87C43457 for ; Mon, 19 Oct 2020 10:27:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4B53820885 for ; Mon, 19 Oct 2020 10:27:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WD8Iz/ha" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726882AbgJSK1S (ORCPT ); Mon, 19 Oct 2020 06:27:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:52204 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726883AbgJSK1Q (ORCPT ); Mon, 19 Oct 2020 06:27:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603103235; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WBzpiSVOvbHp+nYghgN2sMC6AfToSVt2rCZNa5vt8wY=; b=WD8Iz/hah9U4uKAPiZOpn6f3IWpla7JgrUrZfUuS4/UEo7fVJkCQSwOwB5Dq9NoKV0RBFH 2em/OBZ3LOGBLukMWX+qjWJJl9BwIVL7xCDRo0MG7OH+TwiTyynVM1zGVvx7R7KQsNxvyE bfy+VVGpJxsNF3A5MZNrRCbAIWKRutI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-205-OAOQZn7hOpiSDwqxQJp9PA-1; Mon, 19 Oct 2020 06:27:11 -0400 X-MC-Unique: OAOQZn7hOpiSDwqxQJp9PA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 74326425D5; Mon, 19 Oct 2020 10:27:09 +0000 (UTC) Received: from lithium.redhat.com (ovpn-115-42.ams2.redhat.com [10.36.115.42]) by smtp.corp.redhat.com (Postfix) with ESMTP id B31A950B44; Mon, 19 Oct 2020 10:27:07 +0000 (UTC) From: Giuseppe Scrivano To: linux-kernel@vger.kernel.org Cc: linux@rasmusvillemoes.dk, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, christian.brauner@ubuntu.com, containers@lists.linux-foundation.org Subject: [PATCH v2 1/2] fs, close_range: add flag CLOSE_RANGE_CLOEXEC Date: Mon, 19 Oct 2020 12:26:53 +0200 Message-Id: <20201019102654.16642-2-gscrivan@redhat.com> In-Reply-To: <20201019102654.16642-1-gscrivan@redhat.com> References: <20201019102654.16642-1-gscrivan@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When the flag CLOSE_RANGE_CLOEXEC is set, close_range doesn't immediately close the files but it sets the close-on-exec bit. It is useful for e.g. container runtimes that usually install a seccomp profile "as late as possible" before execv'ing the container process itself. The container runtime could either do: 1 2 - install_seccomp_profile(); - close_range(MIN_FD, MAX_INT, 0); - close_range(MIN_FD, MAX_INT, 0); - install_seccomp_profile(); - execve(...); - execve(...); Both alternative have some disadvantages. In the first variant the seccomp_profile cannot block the close_range syscall, as well as opendir/read/close/... for the fallback on older kernels). In the second variant, close_range() can be used only on the fds that are not going to be needed by the runtime anymore, and it must be potentially called multiple times to account for the different ranges that must be closed. Using close_range(..., ..., CLOSE_RANGE_CLOEXEC) solves these issues. The runtime is able to use the open fds and the seccomp profile could block close_range() and the syscalls used for its fallback. Signed-off-by: Giuseppe Scrivano --- fs/file.c | 44 ++++++++++++++++++++++++-------- include/uapi/linux/close_range.h | 3 +++ 2 files changed, 37 insertions(+), 10 deletions(-) diff --git a/fs/file.c b/fs/file.c index 21c0893f2f1d..0295d4f7c5ef 100644 --- a/fs/file.c +++ b/fs/file.c @@ -672,6 +672,35 @@ int __close_fd(struct files_struct *files, unsigned fd) } EXPORT_SYMBOL(__close_fd); /* for ksys_close() */ +static inline void __range_cloexec(struct files_struct *cur_fds, + unsigned int fd, unsigned int max_fd) +{ + struct fdtable *fdt; + + if (fd > max_fd) + return; + + spin_lock(&cur_fds->file_lock); + fdt = files_fdtable(cur_fds); + bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1); + spin_unlock(&cur_fds->file_lock); +} + +static inline void __range_close(struct files_struct *cur_fds, unsigned int fd, + unsigned int max_fd) +{ + while (fd <= max_fd) { + struct file *file; + + file = pick_file(cur_fds, fd++); + if (!file) + continue; + + filp_close(file, cur_fds); + cond_resched(); + } +} + /** * __close_range() - Close all file descriptors in a given range. * @@ -687,7 +716,7 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) struct task_struct *me = current; struct files_struct *cur_fds = me->files, *fds = NULL; - if (flags & ~CLOSE_RANGE_UNSHARE) + if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC)) return -EINVAL; if (fd > max_fd) @@ -725,16 +754,11 @@ int __close_range(unsigned fd, unsigned max_fd, unsigned int flags) } max_fd = min(max_fd, cur_max); - while (fd <= max_fd) { - struct file *file; - file = pick_file(cur_fds, fd++); - if (!file) - continue; - - filp_close(file, cur_fds); - cond_resched(); - } + if (flags & CLOSE_RANGE_CLOEXEC) + __range_cloexec(cur_fds, fd, max_fd); + else + __range_close(cur_fds, fd, max_fd); if (fds) { /* diff --git a/include/uapi/linux/close_range.h b/include/uapi/linux/close_range.h index 6928a9fdee3c..2d804281554c 100644 --- a/include/uapi/linux/close_range.h +++ b/include/uapi/linux/close_range.h @@ -5,5 +5,8 @@ /* Unshare the file descriptor table before closing file descriptors. */ #define CLOSE_RANGE_UNSHARE (1U << 1) +/* Set the FD_CLOEXEC bit instead of closing the file descriptor. */ +#define CLOSE_RANGE_CLOEXEC (1U << 2) + #endif /* _UAPI_LINUX_CLOSE_RANGE_H */ -- 2.26.2