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=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 45D84C04A6B for ; Wed, 8 May 2019 15:25:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F04E620989 for ; Wed, 8 May 2019 15:25:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=brauner.io header.i=@brauner.io header.b="DfgiVosd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727837AbfEHPZ1 (ORCPT ); Wed, 8 May 2019 11:25:27 -0400 Received: from mail-ed1-f66.google.com ([209.85.208.66]:35850 "EHLO mail-ed1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726824AbfEHPZ1 (ORCPT ); Wed, 8 May 2019 11:25:27 -0400 Received: by mail-ed1-f66.google.com with SMTP id a8so22464599edx.3 for ; Wed, 08 May 2019 08:25:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brauner.io; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=qvU/Fga2oBqDEMkiDkNMaTtUf1nAg286SrTOaFtZTkU=; b=DfgiVosd0Wpp8tCt4AMLt1wEIFDaDkuwlOPGwtb5KlMHx+LbFacc/uBuD0Wkhoa/xF 1CtKBsVkkm9DrZ6vnKzDzUixLp96JzmN/wLluiDTslV8KI/RCGsaFwizkS81bQt+700x 2EvdaPr2P3SGHjwN9RnLwkDteD7ifG+QX0R7o//PCfiAsCkslVrinLbOD2TTTMxEmdjX DjlgYzXGnSHWbSmQhV2xiizG8CLa3Q//RcURlRXPA8Qu1uXjYEF1dLZKbh69/xLSuVVd 4W5LRB6n91X8EAxVkc97M+r55lqv7IDB4+njcLIpAocfJ4aqf9+GXzsbWTKMUNiU0Jse TFTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=qvU/Fga2oBqDEMkiDkNMaTtUf1nAg286SrTOaFtZTkU=; b=uXPrk13FneAxELMCp/WrAv4wE7p18nWtGKYZeNuZDPeXGZhlNWaZfYIfuOE67eRbCQ kmLkof4osSBw0p+AyE7rb+qG0MdWvocdpDevpBWSaUNQPSRMOFfB+pXOs8/42TBuwCAc htahkPNkKPHeEkqI7YXIxiBVDXW7MSNjPUIVg9kNjvoFAw32vNO1ucd80Np32ZCwzfP4 41tUfeAq1wqMbpkkVKee7QwLlgTqT5Qo+RVwG3T7m2FQ9dfIiq3fAsWGEBF7X9ySR5sA u3k23h89YE9a2gyfzALVqMWGW+W7ELdKSdxjHT2vHUDqMpanS1E/WtR7RdER+r7XbWyR zbOA== X-Gm-Message-State: APjAAAUpr9t8HGR88jaYTFhRX7DGIY6Dp8oR+DPJGtQwxEEcAz5S350W Sn6G7u2Spp36wQ2gsCYhIvZHzQ== X-Google-Smtp-Source: APXvYqzl7YESAk155xiF/5CTQ2LEbpfPrgqc8hm7xOX3oHwApf4tefIAE+kp3SMzHo7YKRJlwF81ew== X-Received: by 2002:a50:a4f7:: with SMTP id x52mr40383308edb.86.1557329125458; Wed, 08 May 2019 08:25:25 -0700 (PDT) Received: from localhost.localdomain ([212.91.227.56]) by smtp.gmail.com with ESMTPSA id r55sm5260252edd.94.2019.05.08.08.25.23 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 May 2019 08:25:24 -0700 (PDT) From: Christian Brauner To: viro@zeniv.linux.org.uk, dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Christian Brauner Subject: [PATCH v1 1/2] fs: make all new mount api fds cloexec by default Date: Wed, 8 May 2019 17:25:08 +0200 Message-Id: <20190508152509.13336-1-christian@brauner.io> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This makes all file descriptors returned from new syscalls of the new mount api cloexec by default. >From a userspace perspective it is rarely the case that fds are supposed to be inherited across exec. In fact, most of the time userspace either needs to remember to pass the _CLOEXEC flag along or needs to invoke fcntl() on the fd to prevent leaking the fd. This is a much bigger issue than forgetting to remove the cloexec flag to inherit the fd. For old fd types we can't break userspace. But for new ones we should whenever reasonable make them cloexec by default (Examples of this policy are the new seccomp notify fds and also pidfds.). If userspace wants to inherit fds across exec they can remove the O_CLOEXEC flag and need to opt in to inheritance explicitly. Note, this also has the advantage that we can get rid of all the special flags per file descriptor type for the new mount api. In total this lets us remove 4 flags: - FSMOUNT_CLOEXEC - FSOPEN_CLOEXEC - FSPICK_CLOEXEC - OPEN_TREE_CLOEXEC Signed-off-by: Christian Brauner --- v1: - David Howells : - ensure that only O_CLOEXEC is passed so that fd allocation doesn't break when new flags are added to a syscall --- fs/fsopen.c | 13 ++++++------- fs/namespace.c | 11 ++++------- include/uapi/linux/mount.h | 18 +++--------------- 3 files changed, 13 insertions(+), 29 deletions(-) diff --git a/fs/fsopen.c b/fs/fsopen.c index 3bb9c0c8cbcc..a38fa8c616cf 100644 --- a/fs/fsopen.c +++ b/fs/fsopen.c @@ -88,12 +88,12 @@ const struct file_operations fscontext_fops = { /* * Attach a filesystem context to a file and an fd. */ -static int fscontext_create_fd(struct fs_context *fc, unsigned int o_flags) +static int fscontext_create_fd(struct fs_context *fc) { int fd; fd = anon_inode_getfd("fscontext", &fscontext_fops, fc, - O_RDWR | o_flags); + O_RDWR | O_CLOEXEC); if (fd < 0) put_fs_context(fc); return fd; @@ -126,7 +126,7 @@ SYSCALL_DEFINE2(fsopen, const char __user *, _fs_name, unsigned int, flags) if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; - if (flags & ~FSOPEN_CLOEXEC) + if (flags) return -EINVAL; fs_name = strndup_user(_fs_name, PAGE_SIZE); @@ -149,7 +149,7 @@ SYSCALL_DEFINE2(fsopen, const char __user *, _fs_name, unsigned int, flags) if (ret < 0) goto err_fc; - return fscontext_create_fd(fc, flags & FSOPEN_CLOEXEC ? O_CLOEXEC : 0); + return fscontext_create_fd(fc); err_fc: put_fs_context(fc); @@ -169,8 +169,7 @@ SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) return -EPERM; - if ((flags & ~(FSPICK_CLOEXEC | - FSPICK_SYMLINK_NOFOLLOW | + if ((flags & ~(FSPICK_SYMLINK_NOFOLLOW | FSPICK_NO_AUTOMOUNT | FSPICK_EMPTY_PATH)) != 0) return -EINVAL; @@ -203,7 +202,7 @@ SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags goto err_fc; path_put(&target); - return fscontext_create_fd(fc, flags & FSPICK_CLOEXEC ? O_CLOEXEC : 0); + return fscontext_create_fd(fc); err_fc: put_fs_context(fc); diff --git a/fs/namespace.c b/fs/namespace.c index 3357c3d65475..b024e2a05384 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2369,11 +2369,8 @@ SYSCALL_DEFINE3(open_tree, int, dfd, const char *, filename, unsigned, flags) int error; int fd; - BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC); - if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE | - AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE | - OPEN_TREE_CLOEXEC)) + AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE)) return -EINVAL; if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE) @@ -2389,7 +2386,7 @@ SYSCALL_DEFINE3(open_tree, int, dfd, const char *, filename, unsigned, flags) if (detached && !may_mount()) return -EPERM; - fd = get_unused_fd_flags(flags & O_CLOEXEC); + fd = get_unused_fd_flags(O_CLOEXEC); if (fd < 0) return fd; @@ -3352,7 +3349,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, if (!may_mount()) return -EPERM; - if ((flags & ~(FSMOUNT_CLOEXEC)) != 0) + if (flags) return -EINVAL; if (attr_flags & ~(MOUNT_ATTR_RDONLY | @@ -3457,7 +3454,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, } file->f_mode |= FMODE_NEED_UNMOUNT; - ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0); + ret = get_unused_fd_flags(O_CLOEXEC); if (ret >= 0) fd_install(ret, file); else diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h index 96a0240f23fe..c688e4ac843b 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -59,7 +59,6 @@ * open_tree() flags. */ #define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */ -#define OPEN_TREE_CLOEXEC O_CLOEXEC /* Close the file on execve() */ /* * move_mount() flags. @@ -72,18 +71,12 @@ #define MOVE_MOUNT_T_EMPTY_PATH 0x00000040 /* Empty to path permitted */ #define MOVE_MOUNT__MASK 0x00000077 -/* - * fsopen() flags. - */ -#define FSOPEN_CLOEXEC 0x00000001 - /* * fspick() flags. */ -#define FSPICK_CLOEXEC 0x00000001 -#define FSPICK_SYMLINK_NOFOLLOW 0x00000002 -#define FSPICK_NO_AUTOMOUNT 0x00000004 -#define FSPICK_EMPTY_PATH 0x00000008 +#define FSPICK_SYMLINK_NOFOLLOW 0x00000001 +#define FSPICK_NO_AUTOMOUNT 0x00000002 +#define FSPICK_EMPTY_PATH 0x00000004 /* * The type of fsconfig() call made. @@ -99,11 +92,6 @@ enum fsconfig_command { FSCONFIG_CMD_RECONFIGURE = 7, /* Invoke superblock reconfiguration */ }; -/* - * fsmount() flags. - */ -#define FSMOUNT_CLOEXEC 0x00000001 - /* * Mount attributes. */ -- 2.21.0