From patchwork Wed Aug 1 15:26:55 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 10552531 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0E58A157D for ; Wed, 1 Aug 2018 15:27:07 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F187A2B7C0 for ; Wed, 1 Aug 2018 15:27:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E51B72B7C7; Wed, 1 Aug 2018 15:27:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2B7782B7C0 for ; Wed, 1 Aug 2018 15:27:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389926AbeHARNL (ORCPT ); Wed, 1 Aug 2018 13:13:11 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:45312 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389725AbeHARNL (ORCPT ); Wed, 1 Aug 2018 13:13:11 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B3E9240214E2; Wed, 1 Aug 2018 15:26:56 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-116.rdu2.redhat.com [10.10.120.116]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8D14D10FFE6A; Wed, 1 Aug 2018 15:26:55 +0000 (UTC) Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 25/33] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #11] From: David Howells To: viro@zeniv.linux.org.uk Cc: linux-api@vger.kernel.org, torvalds@linux-foundation.org, dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 01 Aug 2018 16:26:55 +0100 Message-ID: <153313721502.13253.3832224933035012490.stgit@warthog.procyon.org.uk> In-Reply-To: <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk> References: <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Wed, 01 Aug 2018 15:26:56 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Wed, 01 Aug 2018 15:26:56 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'dhowells@redhat.com' RCPT:'' Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Provide an fsopen() system call that starts the process of preparing to create a superblock that will then be mountable, using an fd as a context handle. fsopen() is given the name of the filesystem that will be used: int mfd = fsopen(const char *fsname, unsigned int flags); where flags can be 0 or FSOPEN_CLOEXEC. For example: sfd = fsopen("ext4", FSOPEN_CLOEXEC); fsconfig(sfd, FSCONFIG_SET_PATH, "source", "/dev/sda1", AT_FDCWD); fsconfig(sfd, FSCONFIG_SET_FLAG, "noatime", NULL, 0); fsconfig(sfd, FSCONFIG_SET_FLAG, "acl", NULL, 0); fsconfig(sfd, FSCONFIG_SET_FLAG, "user_xattr", NULL, 0); fsconfig(sfd, FSCONFIG_SET_STRING, "sb", "1", 0); fsconfig(sfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); fsinfo(sfd, NULL, ...); // query new superblock attributes mfd = fsmount(sfd, FSMOUNT_CLOEXEC, MS_RELATIME); move_mount(mfd, "", sfd, AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH); sfd = fsopen("afs", -1); fsconfig(fd, FSCONFIG_SET_STRING, "source", "#grand.central.org:root.cell", 0); fsconfig(fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0); mfd = fsmount(sfd, 0, MS_NODEV); move_mount(mfd, "", sfd, AT_FDCWD, "/mnt", MOVE_MOUNT_F_EMPTY_PATH); If an error is reported at any step, an error message may be available to be read() back (ENODATA will be reported if there isn't an error available) in the form: "e :" "e SELinux:Mount on mountpoint not permitted" Once fsmount() has been called, further fsconfig() calls will incur EBUSY, even if the fsmount() fails. read() is still possible to retrieve error information. The fsopen() syscall creates a mount context and hangs it of the fd that it returns. Netlink is not used because it is optional and would make the core VFS dependent on the networking layer and also potentially add network namespace issues. Note that, for the moment, the caller must have SYS_CAP_ADMIN to use fsopen(). Signed-off-by: David Howells cc: linux-api@vger.kernel.org --- arch/x86/entry/syscalls/syscall_32.tbl | 1 arch/x86/entry/syscalls/syscall_64.tbl | 1 fs/Makefile | 2 - fs/fs_context.c | 4 + fs/fsopen.c | 87 ++++++++++++++++++++++++++++++++ include/linux/fs_context.h | 4 + include/linux/syscalls.h | 1 include/uapi/linux/fs.h | 5 ++ 8 files changed, 104 insertions(+), 1 deletion(-) create mode 100644 fs/fsopen.c diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 76d092b7d1b0..1647fefd2969 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -400,3 +400,4 @@ 386 i386 rseq sys_rseq __ia32_sys_rseq 387 i386 open_tree sys_open_tree __ia32_sys_open_tree 388 i386 move_mount sys_move_mount __ia32_sys_move_mount +389 i386 fsopen sys_fsopen __ia32_sys_fsopen diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 37ba4e65eee6..235d33dbccb2 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -345,6 +345,7 @@ 334 common rseq __x64_sys_rseq 335 common open_tree __x64_sys_open_tree 336 common move_mount __x64_sys_move_mount +337 common fsopen __x64_sys_fsopen # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/fs/Makefile b/fs/Makefile index ae681523b4b1..e3ea8093b178 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -13,7 +13,7 @@ obj-y := open.o read_write.o file_table.o super.o \ seq_file.o xattr.o libfs.o fs-writeback.o \ pnode.o splice.o sync.o utimes.o d_path.o \ stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \ - fs_context.o fs_parser.o + fs_context.o fs_parser.o fsopen.o ifeq ($(CONFIG_BLOCK),y) obj-y += buffer.o block_dev.o direct-io.o mpage.o diff --git a/fs/fs_context.c b/fs/fs_context.c index 8f040a20b320..90db81d7008c 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -263,6 +263,8 @@ struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type, fc->fs_type = get_filesystem(fs_type); fc->cred = get_current_cred(); + mutex_init(&fc->uapi_mutex); + switch (purpose) { case FS_CONTEXT_FOR_KERNEL_MOUNT: fc->sb_flags |= SB_KERNMOUNT; @@ -348,6 +350,8 @@ struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc) if (!fc) return ERR_PTR(-ENOMEM); + mutex_init(&fc->uapi_mutex); + fc->fs_private = NULL; fc->s_fs_info = NULL; fc->source = NULL; diff --git a/fs/fsopen.c b/fs/fsopen.c new file mode 100644 index 000000000000..f30080e1ebc4 --- /dev/null +++ b/fs/fsopen.c @@ -0,0 +1,87 @@ +/* Filesystem access-by-fd. + * + * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include "mount.h" + +static int fscontext_release(struct inode *inode, struct file *file) +{ + struct fs_context *fc = file->private_data; + + if (fc) { + file->private_data = NULL; + put_fs_context(fc); + } + return 0; +} + +const struct file_operations fscontext_fops = { + .release = fscontext_release, + .llseek = no_llseek, +}; + +/* + * Attach a filesystem context to a file and an fd. + */ +static int fscontext_create_fd(struct fs_context *fc, unsigned int o_flags) +{ + int fd; + + fd = anon_inode_getfd("fscontext", &fscontext_fops, fc, + O_RDWR | o_flags); + if (fd < 0) + put_fs_context(fc); + return fd; +} + +/* + * Open a filesystem by name so that it can be configured for mounting. + * + * We are allowed to specify a container in which the filesystem will be + * opened, thereby indicating which namespaces will be used (notably, which + * network namespace will be used for network filesystems). + */ +SYSCALL_DEFINE2(fsopen, const char __user *, _fs_name, unsigned int, flags) +{ + struct file_system_type *fs_type; + struct fs_context *fc; + const char *fs_name; + + if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + if (flags & ~FSOPEN_CLOEXEC) + return -EINVAL; + + fs_name = strndup_user(_fs_name, PAGE_SIZE); + if (IS_ERR(fs_name)) + return PTR_ERR(fs_name); + + fs_type = get_fs_type(fs_name); + kfree(fs_name); + if (!fs_type) + return -ENODEV; + + fc = vfs_new_fs_context(fs_type, NULL, 0, FS_CONTEXT_FOR_USER_MOUNT); + put_filesystem(fs_type); + if (IS_ERR(fc)) + return PTR_ERR(fc); + + fc->phase = FS_CONTEXT_CREATE_PARAMS; + return fscontext_create_fd(fc, flags & FSOPEN_CLOEXEC ? O_CLOEXEC : 0); +} diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index bbb8114f2fdc..5445889f705b 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -14,6 +14,7 @@ #include #include +#include struct cred; struct dentry; @@ -87,6 +88,7 @@ struct fs_parameter { */ struct fs_context { const struct fs_context_operations *ops; + struct mutex uapi_mutex; /* Userspace access mutex */ struct file_system_type *fs_type; void *fs_private; /* The filesystem's context */ struct dentry *root; /* The root and superblock */ @@ -143,6 +145,8 @@ extern int vfs_get_super(struct fs_context *fc, int (*fill_super)(struct super_block *sb, struct fs_context *fc)); +extern const struct file_operations fscontext_fops; + #define logfc(FC, FMT, ...) pr_notice(FMT, ## __VA_ARGS__) /** diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 3c0855d9b105..ad6c7ff33c01 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -904,6 +904,7 @@ asmlinkage long sys_open_tree(int dfd, const char __user *path, unsigned flags); asmlinkage long sys_move_mount(int from_dfd, const char __user *from_path, int to_dfd, const char __user *to_path, unsigned int ms_flags); +asmlinkage long sys_fsopen(const char __user *fs_name, unsigned int flags); /* * Architecture-specific system calls diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 1c982eb44ff4..f8818e6cddd6 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -344,4 +344,9 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND) +/* + * Flags for fsopen() and co. + */ +#define FSOPEN_CLOEXEC 0x00000001 + #endif /* _UAPI_LINUX_FS_H */