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;	/* Linux S&M 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	unsigned int		lsm_flags;	/* Information flags from the fs to the LSM */
108	enum fs_context_purpose	purpose:8;
109	enum fs_context_phase	phase:8;	/* The phase the context is in */
110	bool			need_free:1;	/* Need to call ops->free() */
111	bool			global:1;	/* Goes into &init_user_ns */
112	bool			oldapi:1;	/* Coming from mount(2) */
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);
139extern int generic_parse_monolithic(struct fs_context *fc, void *data);
140extern int vfs_get_tree(struct fs_context *fc);
141extern void put_fs_context(struct fs_context *fc);
142
143/*
144 * sget() wrappers to be called from the ->get_tree() op.
145 */
146enum vfs_get_super_keying {
147	vfs_get_single_super,	/* Only one such superblock may exist */
148	vfs_get_single_reconf_super, /* As above, but reconfigure if it exists */
149	vfs_get_keyed_super,	/* Superblocks with different s_fs_info keys may exist */
150	vfs_get_independent_super, /* Multiple independent superblocks may exist */
151};
152extern int vfs_get_super(struct fs_context *fc,
153			 enum vfs_get_super_keying keying,
154			 int (*fill_super)(struct super_block *sb,
155					   struct fs_context *fc));
156
157extern int get_tree_nodev(struct fs_context *fc,
158			 int (*fill_super)(struct super_block *sb,
159					   struct fs_context *fc));
160extern int get_tree_single(struct fs_context *fc,
161			 int (*fill_super)(struct super_block *sb,
162					   struct fs_context *fc));
163extern int get_tree_single_reconf(struct fs_context *fc,
164			 int (*fill_super)(struct super_block *sb,
165					   struct fs_context *fc));
166extern int get_tree_keyed(struct fs_context *fc,
167			 int (*fill_super)(struct super_block *sb,
168					   struct fs_context *fc),
169			 void *key);
170
171extern int get_tree_bdev(struct fs_context *fc,
172			       int (*fill_super)(struct super_block *sb,
173						 struct fs_context *fc));
174
175extern const struct file_operations fscontext_fops;
176
177/*
178 * Mount error, warning and informational message logging.  This structure is
179 * shareable between a mount and a subordinate mount.
180 */
181struct fc_log {
182	refcount_t	usage;
183	u8		head;		/* Insertion index in buffer[] */
184	u8		tail;		/* Removal index in buffer[] */
185	u8		need_free;	/* Mask of kfree'able items in buffer[] */
186	struct module	*owner;		/* Owner module for strings that don't then need freeing */
187	char		*buffer[8];
188};
189
190extern __attribute__((format(printf, 4, 5)))
191void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...);
192
193#define __logfc(fc, l, fmt, ...) logfc((fc)->log.log, NULL, \
194					l, fmt, ## __VA_ARGS__)
195#define __plog(p, l, fmt, ...) logfc((p)->log, (p)->prefix, \
196					l, fmt, ## __VA_ARGS__)
197/**
198 * infof - Store supplementary informational message
199 * @fc: The context in which to log the informational message
200 * @fmt: The format string
201 *
202 * Store the supplementary informational message for the process if the process
203 * has enabled the facility.
204 */
205#define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__)
206#define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__)
207#define infofc(p, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__)
208
209/**
210 * warnf - Store supplementary warning message
211 * @fc: The context in which to log the error message
212 * @fmt: The format string
213 *
214 * Store the supplementary warning message for the process if the process has
215 * enabled the facility.
216 */
217#define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__)
218#define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__)
219#define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__)
220
221/**
222 * errorf - Store supplementary error message
223 * @fc: The context in which to log the error message
224 * @fmt: The format string
225 *
226 * Store the supplementary error message for the process if the process has
227 * enabled the facility.
228 */
229#define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__)
230#define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__)
231#define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS__)
232
233/**
234 * invalf - Store supplementary invalid argument error message
235 * @fc: The context in which to log the error message
236 * @fmt: The format string
237 *
238 * Store the supplementary error message for the process if the process has
239 * enabled the facility and return -EINVAL.
240 */
241#define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL)
242#define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINVAL)
243#define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL)
244
245#endif /* _LINUX_FS_CONTEXT_H */