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_filename_empty, /* Value is a filename* + dirfd + AT_EMPTY_PATH */
58 fs_value_is_file, /* Value is a file* */
59 };
60
61 /*
62 * Configuration parameter.
63 */
64 struct fs_parameter {
65 const char *key; /* Parameter name */
66 enum fs_value_type type:8; /* The type of value here */
67 union {
68 char *string;
69 void *blob;
70 struct filename *name;
71 struct file *file;
72 };
73 size_t size;
74 int dirfd;
75 };
76
77 /*
78 * Filesystem context for holding the parameters used in the creation or
79 * reconfiguration of a superblock.
80 *
81 * Superblock creation fills in ->root whereas reconfiguration begins with this
82 * already set.
83 *
84 * See Documentation/filesystems/mount_api.txt
85 */
86 struct fs_context {
87 const struct fs_context_operations *ops;
88 struct mutex uapi_mutex; /* Userspace access mutex */
89 struct file_system_type *fs_type;
90 void *fs_private; /* The filesystem's context */
91 void *sget_key;
92 struct dentry *root; /* The root and superblock */
93 struct user_namespace *user_ns; /* The user namespace for this mount */
94 struct net *net_ns; /* The network namespace for this mount */
95 const struct cred *cred; /* The mounter's credentials */
96 struct fc_log *log; /* Logging buffer */
97 const char *source; /* The source name (eg. dev path) */
98 void *security; /* Linux S&M options */
99 void *s_fs_info; /* Proposed s_fs_info */
100 unsigned int sb_flags; /* Proposed superblock flags (SB_*) */
101 unsigned int sb_flags_mask; /* Superblock flags that were changed */
102 unsigned int s_iflags; /* OR'd with sb->s_iflags */
103 unsigned int lsm_flags; /* Information flags from the fs to the LSM */
104 enum fs_context_purpose purpose:8;
105 enum fs_context_phase phase:8; /* The phase the context is in */
106 bool need_free:1; /* Need to call ops->free() */
107 bool global:1; /* Goes into &init_user_ns */
108 };
109
110 struct fs_context_operations {
111 void (*free)(struct fs_context *fc);
112 int (*dup)(struct fs_context *fc, struct fs_context *src_fc);
113 int (*parse_param)(struct fs_context *fc, struct fs_parameter *param);
114 int (*parse_monolithic)(struct fs_context *fc, void *data);
115 int (*get_tree)(struct fs_context *fc);
116 int (*reconfigure)(struct fs_context *fc);
117 };
118
119 /*
120 * fs_context manipulation functions.
121 */
122 extern struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
123 unsigned int sb_flags);
124 extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
125 unsigned int sb_flags,
126 unsigned int sb_flags_mask);
127 extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,
128 struct dentry *reference);
129
130 extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
131 extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
132 extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
133 const char *value, size_t v_size);
134 extern int generic_parse_monolithic(struct fs_context *fc, void *data);
135 extern int vfs_get_tree(struct fs_context *fc);
136 extern void put_fs_context(struct fs_context *fc);
137
138 /*
139 * sget() wrappers to be called from the ->get_tree() op.
140 */
141 enum vfs_get_super_keying {
142 vfs_get_single_super, /* Only one such superblock may exist */
143 vfs_get_single_reconf_super, /* As above, but reconfigure if it exists */
144 vfs_get_keyed_super, /* Superblocks with different s_fs_info keys may exist */
145 vfs_get_independent_super, /* Multiple independent superblocks may exist */
146 };
147 extern int vfs_get_super(struct fs_context *fc,
148 enum vfs_get_super_keying keying,
149 int (*fill_super)(struct super_block *sb,
150 struct fs_context *fc));
151
152 extern int get_tree_nodev(struct fs_context *fc,
153 int (*fill_super)(struct super_block *sb,
154 struct fs_context *fc));
155 extern int get_tree_single(struct fs_context *fc,
156 int (*fill_super)(struct super_block *sb,
157 struct fs_context *fc));
158 extern int get_tree_single_reconf(struct fs_context *fc,
159 int (*fill_super)(struct super_block *sb,
160 struct fs_context *fc));
161 extern int get_tree_keyed(struct fs_context *fc,
162 int (*fill_super)(struct super_block *sb,
163 struct fs_context *fc),
164 void *key);
165
166 extern int get_tree_bdev(struct fs_context *fc,
167 int (*fill_super)(struct super_block *sb,
168 struct fs_context *fc));
169
170 extern const struct file_operations fscontext_fops;
171
172 /*
173 * Mount error, warning and informational message logging. This structure is
174 * shareable between a mount and a subordinate mount.
175 */
176 struct fc_log {
177 refcount_t usage;
178 u8 head; /* Insertion index in buffer[] */
179 u8 tail; /* Removal index in buffer[] */
180 u8 need_free; /* Mask of kfree'able items in buffer[] */
181 struct module *owner; /* Owner module for strings that don't then need freeing */
182 char *buffer[8];
183 };
184
185 extern __attribute__((format(printf, 2, 3)))
186 void logfc(struct fs_context *fc, const char *fmt, ...);
187
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
198 /**
199 * warnf - Store supplementary warning message
200 * @fc: The context in which to log the error message
201 * @fmt: The format string
202 *
203 * Store the supplementary warning message for the process if the process has
204 * enabled the facility.
205 */
206 #define warnf(fc, fmt, ...) ({ logfc(fc, "w "fmt, ## __VA_ARGS__); })
207
208 /**
209 * errorf - Store supplementary error message
210 * @fc: The context in which to log the error message
211 * @fmt: The format string
212 *
213 * Store the supplementary error message for the process if the process has
214 * enabled the facility.
215 */
216 #define errorf(fc, fmt, ...) ({ logfc(fc, "e "fmt, ## __VA_ARGS__); })
217
218 /**
219 * invalf - Store supplementary invalid argument error message
220 * @fc: The context in which to log the error message
221 * @fmt: The format string
222 *
223 * Store the supplementary error message for the process if the process has
224 * enabled the facility and return -EINVAL.
225 */
226 #define invalf(fc, fmt, ...) ({ errorf(fc, fmt, ## __VA_ARGS__); -EINVAL; })
227
228 #endif /* _LINUX_FS_CONTEXT_H */