[05/10] vfs: syscall: Add fsopen() to prepare for superblock creation

Message ID	155059614302.17079.1281132139815655428.stgit@warthog.procyon.org.uk (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-security-module-owner@kernel.org> Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 05/10] vfs: syscall: Add fsopen() to prepare for superblock creation From: David Howells <dhowells@redhat.com> To: viro@zeniv.linux.org.uk Cc: linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, dhowells@redhat.com, torvalds@linux-foundation.org, ebiederm@xmission.com, linux-security-module@vger.kernel.org Date: Tue, 19 Feb 2019 17:09:03 +0000 Message-ID: <155059614302.17079.1281132139815655428.stgit@warthog.procyon.org.uk> In-Reply-To: <155059610368.17079.2220554006494174417.stgit@warthog.procyon.org.uk> References: <155059610368.17079.2220554006494174417.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk
Series	VFS: Provide new mount UAPI \| expand [00/10] VFS: Provide new mount UAPI [01/10] vfs: syscall: Add open_tree(2) to reference or clone a mount [02/10] vfs: syscall: Add move_mount(2) to move mounts around [03/10] teach move_mount(2) to work with OPEN_TREE_CLONE [04/10] Make anon_inodes unconditional [05/10] vfs: syscall: Add fsopen() to prepare for superblock creation [06/10] vfs: Implement logging through fs_context [07/10] vfs: syscall: Add fsconfig() for configuring and managing a context [08/10] vfs: syscall: Add fsmount() to create a mount for a superblock [09/10] vfs: syscall: Add fspick() to select a superblock for reconfiguration [10/10] vfs: Add a sample program for the new mount API

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 87e3546b9a52..eb806fae3117 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -271,6 +271,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type, fc->cred = get_current_cred(); fc->net_ns = get_net(current->nsproxy->net_ns); + mutex_init(&fc->uapi_mutex); + switch (purpose) { case FS_CONTEXT_FOR_MOUNT: fc->user_ns = get_user_ns(fc->cred->user_ns); @@ -353,6 +355,8 @@ 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..d256f1ac9ff1 --- /dev/null +++ b/fs/fsopen.c @@ -0,0 +1,88 @@ +/* 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 <linux/fs_context.h> +#include <linux/slab.h> +#include <linux/uaccess.h> +#include <linux/syscalls.h> +#include <linux/security.h> +#include <linux/anon_inodes.h> +#include <linux/namei.h> +#include <linux/file.h> +#include <uapi/linux/mount.h> +#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 = fs_context_for_mount(fs_type, 0); + 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 eaca452088fa..7ab8b44fab3e 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -15,6 +15,7 @@ #include <linux/kernel.h> #include <linux/errno.h> #include <linux/security.h> +#include <linux/mutex.h> struct cred; struct dentry; @@ -34,6 +35,19 @@ enum fs_context_purpose { FS_CONTEXT_FOR_RECONFIGURE, /* Superblock reconfiguration (remount) */ }; +/* + * Userspace usage phase for fsopen/fspick. + */ +enum fs_context_phase { + FS_CONTEXT_CREATE_PARAMS, /* Loading params for sb creation */ + FS_CONTEXT_CREATING, /* A superblock is being created */ + FS_CONTEXT_AWAITING_MOUNT, /* Superblock created, awaiting fsmount() */ + FS_CONTEXT_AWAITING_RECONF, /* Awaiting initialisation for reconfiguration */ + FS_CONTEXT_RECONF_PARAMS, /* Loading params for reconfiguration */ + FS_CONTEXT_RECONFIGURING, /* Reconfiguring the superblock */ + FS_CONTEXT_FAILED, /* Failed to correctly transition a context */ +}; + /* * Type of parameter value. */ @@ -74,6 +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 */ @@ -88,6 +103,7 @@ struct fs_context { unsigned int sb_flags_mask; /* Superblock flags that were changed */ unsigned int lsm_flags; /* Information flags from the fs to the LSM */ enum fs_context_purpose purpose:8; + enum fs_context_phase phase:8; /* The phase the context is in */ bool need_free:1; /* Need to call ops->free() */ bool global:1; /* Goes into &init_user_ns */ }; diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 13289cdf6b52..22ed8a11ef55 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -930,6 +930,7 @@ 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/mount.h b/include/uapi/linux/mount.h index 3634e065836c..7570df43d08f 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -72,4 +72,9 @@ #define MOVE_MOUNT_T_EMPTY_PATH 0x00000040 /* Empty to path permitted */ #define MOVE_MOUNT__MASK 0x00000077 +/* + * fsopen() flags. + */ +#define FSOPEN_CLOEXEC 0x00000001 + #endif /* _UAPI_LINUX_MOUNT_H */

[05/10] vfs: syscall: Add fsopen() to prepare for superblock creation

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Patch