1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/* Filesystem superblock creation and reconfiguration context.
3 *
4 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#ifndef _LINUX_FS_CONTEXT_H
9#define _LINUX_FS_CONTEXT_H
10
11#include <linux/kernel.h>
12#include <linux/refcount.h>
13#include <linux/errno.h>
14#include <linux/security.h>
15#include <linux/mutex.h>
16
17struct cred;
18struct dentry;
19struct file_operations;
20struct file_system_type;
21struct mnt_namespace;
22struct net;
23struct pid_namespace;
24struct super_block;
25struct user_namespace;
26struct vfsmount;
27struct path;
28
29enum fs_context_purpose {
30	FS_CONTEXT_FOR_MOUNT,		/* New superblock for explicit mount */
31	FS_CONTEXT_FOR_SUBMOUNT,	/* New superblock for automatic submount */
32	FS_CONTEXT_FOR_RECONFIGURE,	/* Superblock reconfiguration (remount) */
33};
34
35/*
36 * Userspace usage phase for fsopen/fspick.
37 */
38enum fs_context_phase {
39	FS_CONTEXT_CREATE_PARAMS,	/* Loading params for sb creation */
40	FS_CONTEXT_CREATING,		/* A superblock is being created */
41	FS_CONTEXT_AWAITING_MOUNT,	/* Superblock created, awaiting fsmount() */
42	FS_CONTEXT_AWAITING_RECONF,	/* Awaiting initialisation for reconfiguration */
43	FS_CONTEXT_RECONF_PARAMS,	/* Loading params for reconfiguration */
44	FS_CONTEXT_RECONFIGURING,	/* Reconfiguring the superblock */
45	FS_CONTEXT_FAILED,		/* Failed to correctly transition a context */
46};
47
48/*
49 * Type of parameter value.
50 */
51enum fs_value_type {
52	fs_value_is_undefined,
53	fs_value_is_flag,		/* Value not given a value */
54	fs_value_is_string,		/* Value is a string */
55	fs_value_is_blob,		/* Value is a binary blob */
56	fs_value_is_filename,		/* Value is a filename* + dirfd */
57	fs_value_is_file,		/* Value is a file* */
58};
59
60/*
61 * Configuration parameter.
62 */
63struct fs_parameter {
64	const char		*key;		/* Parameter name */
65	enum fs_value_type	type:8;		/* The type of value here */
66	union {
67		char		*string;
68		void		*blob;
69		struct filename	*name;
70		struct file	*file;
71	};
72	size_t	size;
73	int	dirfd;
74};
75
76struct p_log {
77	const char *prefix;
78	struct fc_log *log;
79};
80
81/*
82 * Filesystem context for holding the parameters used in the creation or
83 * reconfiguration of a superblock.
84 *
85 * Superblock creation fills in ->root whereas reconfiguration begins with this
86 * already set.
87 *
88 * See Documentation/filesystems/mount_api.rst
89 */
90struct fs_context {
91	const struct fs_context_operations *ops;
92	struct mutex		uapi_mutex;	/* Userspace access mutex */
93	struct file_system_type	*fs_type;
94	void			*fs_private;	/* The filesystem's context */
95	void			*sget_key;
96	struct dentry		*root;		/* The root and superblock */
97	struct user_namespace	*user_ns;	/* The user namespace for this mount */
98	struct net		*net_ns;	/* The network namespace for this mount */
99	const struct cred	*cred;		/* The mounter's credentials */
100	struct p_log		log;		/* Logging buffer */
101	const char		*source;	/* The source name (eg. dev path) */
102	void			*security;	/* LSM options */
103	void			*s_fs_info;	/* Proposed s_fs_info */
104	unsigned int		sb_flags;	/* Proposed superblock flags (SB_*) */
105	unsigned int		sb_flags_mask;	/* Superblock flags that were changed */
106	unsigned int		s_iflags;	/* OR'd with sb->s_iflags */
107	enum fs_context_purpose	purpose:8;
108	enum fs_context_phase	phase:8;	/* The phase the context is in */
109	bool			need_free:1;	/* Need to call ops->free() */
110	bool			global:1;	/* Goes into &init_user_ns */
111	bool			oldapi:1;	/* Coming from mount(2) */
112	bool			exclusive:1;    /* create new superblock, reject existing one */
113};
114
115struct fs_context_operations {
116	void (*free)(struct fs_context *fc);
117	int (*dup)(struct fs_context *fc, struct fs_context *src_fc);
118	int (*parse_param)(struct fs_context *fc, struct fs_parameter *param);
119	int (*parse_monolithic)(struct fs_context *fc, void *data);
120	int (*get_tree)(struct fs_context *fc);
121	int (*reconfigure)(struct fs_context *fc);
122};
123
124/*
125 * fs_context manipulation functions.
126 */
127extern struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
128						unsigned int sb_flags);
129extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
130						unsigned int sb_flags,
131						unsigned int sb_flags_mask);
132extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,
133						struct dentry *reference);
134
135extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
136extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
137extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
138			       const char *value, size_t v_size);
139int vfs_parse_monolithic_sep(struct fs_context *fc, void *data,
140			     char *(*sep)(char **));
141extern int generic_parse_monolithic(struct fs_context *fc, void *data);
142extern int vfs_get_tree(struct fs_context *fc);
143extern void put_fs_context(struct fs_context *fc);
144extern int vfs_parse_fs_param_source(struct fs_context *fc,
145				     struct fs_parameter *param);
146extern void fc_drop_locked(struct fs_context *fc);
147int reconfigure_single(struct super_block *s,
148		       int flags, void *data);
149
150extern int get_tree_nodev(struct fs_context *fc,
151			 int (*fill_super)(struct super_block *sb,
152					   struct fs_context *fc));
153extern int get_tree_single(struct fs_context *fc,
154			 int (*fill_super)(struct super_block *sb,
155					   struct fs_context *fc));
156extern int get_tree_keyed(struct fs_context *fc,
157			 int (*fill_super)(struct super_block *sb,
158					   struct fs_context *fc),
159			 void *key);
160
161int setup_bdev_super(struct super_block *sb, int sb_flags,
162		struct fs_context *fc);
163extern int get_tree_bdev(struct fs_context *fc,
164			       int (*fill_super)(struct super_block *sb,
165						 struct fs_context *fc));
166
167extern const struct file_operations fscontext_fops;
168
169/*
170 * Mount error, warning and informational message logging.  This structure is
171 * shareable between a mount and a subordinate mount.
172 */
173struct fc_log {
174	refcount_t	usage;
175	u8		head;		/* Insertion index in buffer[] */
176	u8		tail;		/* Removal index in buffer[] */
177	u8		need_free;	/* Mask of kfree'able items in buffer[] */
178	struct module	*owner;		/* Owner module for strings that don't then need freeing */
179	char		*buffer[8];
180};
181
182extern __attribute__((format(printf, 4, 5)))
183void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...);
184
185#define __logfc(fc, l, fmt, ...) logfc((fc)->log.log, NULL, \
186					l, fmt, ## __VA_ARGS__)
187#define __plog(p, l, fmt, ...) logfc((p)->log, (p)->prefix, \
188					l, fmt, ## __VA_ARGS__)
189/**
190 * infof - Store supplementary informational message
191 * @fc: The context in which to log the informational message
192 * @fmt: The format string
193 *
194 * Store the supplementary informational message for the process if the process
195 * has enabled the facility.
196 */
197#define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__)
198#define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__)
199#define infofc(p, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__)
200
201/**
202 * warnf - Store supplementary warning message
203 * @fc: The context in which to log the error message
204 * @fmt: The format string
205 *
206 * Store the supplementary warning message for the process if the process has
207 * enabled the facility.
208 */
209#define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__)
210#define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__)
211#define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__)
212
213/**
214 * errorf - Store supplementary error message
215 * @fc: The context in which to log the error message
216 * @fmt: The format string
217 *
218 * Store the supplementary error message for the process if the process has
219 * enabled the facility.
220 */
221#define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__)
222#define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__)
223#define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS__)
224
225/**
226 * invalf - Store supplementary invalid argument error message
227 * @fc: The context in which to log the error message
228 * @fmt: The format string
229 *
230 * Store the supplementary error message for the process if the process has
231 * enabled the facility and return -EINVAL.
232 */
233#define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL)
234#define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINVAL)
235#define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL)
236
237#endif /* _LINUX_FS_CONTEXT_H */
238