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 
17 struct cred;
18 struct dentry;
19 struct file_operations;
20 struct file_system_type;
21 struct mnt_namespace;
22 struct net;
23 struct pid_namespace;
24 struct super_block;
25 struct user_namespace;
26 struct vfsmount;
27 struct path;
28 
29 enum 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  */
38 enum 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  */
51 enum 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  */
63 struct 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 
76 struct 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  */
90 struct 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 	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 
115 struct 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  */
127 extern struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
128 						unsigned int sb_flags);
129 extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
130 						unsigned int sb_flags,
131 						unsigned int sb_flags_mask);
132 extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,
133 						struct dentry *reference);
134 
135 extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
136 extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
137 extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
138 			       const char *value, size_t v_size);
139 extern int generic_parse_monolithic(struct fs_context *fc, void *data);
140 extern int vfs_get_tree(struct fs_context *fc);
141 extern void put_fs_context(struct fs_context *fc);
142 extern int vfs_parse_fs_param_source(struct fs_context *fc,
143 				     struct fs_parameter *param);
144 extern void fc_drop_locked(struct fs_context *fc);
145 int reconfigure_single(struct super_block *s,
146 		       int flags, void *data);
147 
148 extern int get_tree_nodev(struct fs_context *fc,
149 			 int (*fill_super)(struct super_block *sb,
150 					   struct fs_context *fc));
151 extern int get_tree_single(struct fs_context *fc,
152 			 int (*fill_super)(struct super_block *sb,
153 					   struct fs_context *fc));
154 extern int get_tree_single_reconf(struct fs_context *fc,
155 			 int (*fill_super)(struct super_block *sb,
156 					   struct fs_context *fc));
157 extern int get_tree_keyed(struct fs_context *fc,
158 			 int (*fill_super)(struct super_block *sb,
159 					   struct fs_context *fc),
160 			 void *key);
161 
162 extern int get_tree_bdev(struct fs_context *fc,
163 			       int (*fill_super)(struct super_block *sb,
164 						 struct fs_context *fc));
165 
166 extern const struct file_operations fscontext_fops;
167 
168 /*
169  * Mount error, warning and informational message logging.  This structure is
170  * shareable between a mount and a subordinate mount.
171  */
172 struct fc_log {
173 	refcount_t	usage;
174 	u8		head;		/* Insertion index in buffer[] */
175 	u8		tail;		/* Removal index in buffer[] */
176 	u8		need_free;	/* Mask of kfree'able items in buffer[] */
177 	struct module	*owner;		/* Owner module for strings that don't then need freeing */
178 	char		*buffer[8];
179 };
180 
181 extern __attribute__((format(printf, 4, 5)))
182 void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...);
183 
184 #define __logfc(fc, l, fmt, ...) logfc((fc)->log.log, NULL, \
185 					l, fmt, ## __VA_ARGS__)
186 #define __plog(p, l, fmt, ...) logfc((p)->log, (p)->prefix, \
187 					l, fmt, ## __VA_ARGS__)
188 /**
189  * infof - Store supplementary informational message
190  * @fc: The context in which to log the informational message
191  * @fmt: The format string
192  *
193  * Store the supplementary informational message for the process if the process
194  * has enabled the facility.
195  */
196 #define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__)
197 #define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__)
198 #define infofc(p, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__)
199 
200 /**
201  * warnf - Store supplementary warning message
202  * @fc: The context in which to log the error message
203  * @fmt: The format string
204  *
205  * Store the supplementary warning message for the process if the process has
206  * enabled the facility.
207  */
208 #define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__)
209 #define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__)
210 #define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__)
211 
212 /**
213  * errorf - Store supplementary error message
214  * @fc: The context in which to log the error message
215  * @fmt: The format string
216  *
217  * Store the supplementary error message for the process if the process has
218  * enabled the facility.
219  */
220 #define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__)
221 #define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__)
222 #define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS__)
223 
224 /**
225  * invalf - Store supplementary invalid argument error message
226  * @fc: The context in which to log the error message
227  * @fmt: The format string
228  *
229  * Store the supplementary error message for the process if the process has
230  * enabled the facility and return -EINVAL.
231  */
232 #define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL)
233 #define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINVAL)
234 #define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL)
235 
236 #endif /* _LINUX_FS_CONTEXT_H */
237