fs_context.h

  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_qstr(struct fs_context *fc, const char *key,
138				const struct qstr *value);
139static inline int vfs_parse_fs_string(struct fs_context *fc, const char *key,
140			       const char *value)
141{
142	return vfs_parse_fs_qstr(fc, key, value ? &QSTR(value) : NULL);
143}
144int vfs_parse_monolithic_sep(struct fs_context *fc, void *data,
145			     char *(*sep)(char **));
146extern int generic_parse_monolithic(struct fs_context *fc, void *data);
147extern int vfs_get_tree(struct fs_context *fc);
148extern void put_fs_context(struct fs_context *fc);
149extern int vfs_parse_fs_param_source(struct fs_context *fc,
150				     struct fs_parameter *param);
151extern void fc_drop_locked(struct fs_context *fc);
152
153extern int get_tree_nodev(struct fs_context *fc,
154			 int (*fill_super)(struct super_block *sb,
155					   struct fs_context *fc));
156extern int get_tree_single(struct fs_context *fc,
157			 int (*fill_super)(struct super_block *sb,
158					   struct fs_context *fc));
159extern int get_tree_keyed(struct fs_context *fc,
160			 int (*fill_super)(struct super_block *sb,
161					   struct fs_context *fc),
162			 void *key);
163
164int setup_bdev_super(struct super_block *sb, int sb_flags,
165		struct fs_context *fc);
166
167#define GET_TREE_BDEV_QUIET_LOOKUP		0x0001
168int get_tree_bdev_flags(struct fs_context *fc,
169		int (*fill_super)(struct super_block *sb,
170				  struct fs_context *fc), unsigned int flags);
171
172extern int get_tree_bdev(struct fs_context *fc,
173			       int (*fill_super)(struct super_block *sb,
174						 struct fs_context *fc));
175
176extern const struct file_operations fscontext_fops;
177
178/*
179 * Mount error, warning and informational message logging.  This structure is
180 * shareable between a mount and a subordinate mount.
181 */
182struct fc_log {
183	refcount_t	usage;
184	u8		head;		/* Insertion index in buffer[] */
185	u8		tail;		/* Removal index in buffer[] */
186	u8		need_free;	/* Mask of kfree'able items in buffer[] */
187	struct module	*owner;		/* Owner module for strings that don't then need freeing */
188	char		*buffer[8];
189};
190
191extern __attribute__((format(printf, 4, 5)))
192void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...);
193
194#define __logfc(fc, l, fmt, ...) \
195	logfc((fc)->log.log, NULL, (l), (fmt), ## __VA_ARGS__)
196#define __plogp(p, prefix, l, fmt, ...) \
197	logfc((p)->log, (prefix), (l), (fmt), ## __VA_ARGS__)
198#define __plog(p, l, fmt, ...) __plogp(p, (p)->prefix, l, fmt, ## __VA_ARGS__)
199
200/**
201 * infof - Store supplementary informational message
202 * @fc: The context in which to log the informational message
203 * @fmt: The format string
204 *
205 * Store the supplementary informational message for the process if the process
206 * has enabled the facility.
207 */
208#define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__)
209#define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__)
210#define infofc(fc, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__)
211#define infofcp(fc, prefix, fmt, ...) \
212	__plogp((&(fc)->log), prefix, 'i', fmt, ## __VA_ARGS__)
213
214/**
215 * warnf - Store supplementary warning message
216 * @fc: The context in which to log the error message
217 * @fmt: The format string
218 *
219 * Store the supplementary warning message for the process if the process has
220 * enabled the facility.
221 */
222#define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__)
223#define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__)
224#define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__)
225#define warnfcp(fc, prefix, fmt, ...) \
226	__plogp((&(fc)->log), prefix, 'w', fmt, ## __VA_ARGS__)
227
228/**
229 * errorf - Store supplementary error message
230 * @fc: The context in which to log the error message
231 * @fmt: The format string
232 *
233 * Store the supplementary error message for the process if the process has
234 * enabled the facility.
235 */
236#define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__)
237#define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__)
238#define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS__)
239#define errorfcp(fc, prefix, fmt, ...) \
240	__plogp((&(fc)->log), prefix, 'e', fmt, ## __VA_ARGS__)
241
242/**
243 * invalf - Store supplementary invalid argument error message
244 * @fc: The context in which to log the error message
245 * @fmt: The format string
246 *
247 * Store the supplementary error message for the process if the process has
248 * enabled the facility and return -EINVAL.
249 */
250#define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL)
251#define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINVAL)
252#define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL)
253#define invalfcp(fc, prefix, fmt, ...) \
254	(errorfcp(fc, prefix, fmt, ## __VA_ARGS__), -EINVAL)
255
256#endif /* _LINUX_FS_CONTEXT_H */