include/linux/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
  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.txt
  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;      /* 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 };
 113
 114 struct fs_context_operations {
 115         void (*free)(struct fs_context *fc);
 116         int (*dup)(struct fs_context *fc, struct fs_context *src_fc);
 117         int (*parse_param)(struct fs_context *fc, struct fs_parameter *param);
 118         int (*parse_monolithic)(struct fs_context *fc, void *data);
 119         int (*get_tree)(struct fs_context *fc);
 120         int (*reconfigure)(struct fs_context *fc);
 121 };
 122
 123 /*
 124  * fs_context manipulation functions.
 125  */
 126 extern struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
 127                                                 unsigned int sb_flags);
 128 extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
 129                                                 unsigned int sb_flags,
 130                                                 unsigned int sb_flags_mask);
 131 extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,
 132                                                 struct dentry *reference);
 133
 134 extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
 135 extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
 136 extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
 137                                const char *value, size_t v_size);
 138 extern int generic_parse_monolithic(struct fs_context *fc, void *data);
 139 extern int vfs_get_tree(struct fs_context *fc);
 140 extern void put_fs_context(struct fs_context *fc);
 141
 142 /*
 143  * sget() wrappers to be called from the ->get_tree() op.
 144  */
 145 enum vfs_get_super_keying {
 146         vfs_get_single_super,   /* Only one such superblock may exist */
 147         vfs_get_single_reconf_super, /* As above, but reconfigure if it exists */
 148         vfs_get_keyed_super,    /* Superblocks with different s_fs_info keys may exist */
 149         vfs_get_independent_super, /* Multiple independent superblocks may exist */
 150 };
 151 extern int vfs_get_super(struct fs_context *fc,
 152                          enum vfs_get_super_keying keying,
 153                          int (*fill_super)(struct super_block *sb,
 154                                            struct fs_context *fc));
 155
 156 extern int get_tree_nodev(struct fs_context *fc,
 157                          int (*fill_super)(struct super_block *sb,
 158                                            struct fs_context *fc));
 159 extern int get_tree_single(struct fs_context *fc,
 160                          int (*fill_super)(struct super_block *sb,
 161                                            struct fs_context *fc));
 162 extern int get_tree_single_reconf(struct fs_context *fc,
 163                          int (*fill_super)(struct super_block *sb,
 164                                            struct fs_context *fc));
 165 extern int get_tree_keyed(struct fs_context *fc,
 166                          int (*fill_super)(struct super_block *sb,
 167                                            struct fs_context *fc),
 168                          void *key);
 169
 170 extern int get_tree_bdev(struct fs_context *fc,
 171                                int (*fill_super)(struct super_block *sb,
 172                                                  struct fs_context *fc));
 173
 174 extern const struct file_operations fscontext_fops;
 175
 176 /*
 177  * Mount error, warning and informational message logging.  This structure is
 178  * shareable between a mount and a subordinate mount.
 179  */
 180 struct fc_log {
 181         refcount_t      usage;
 182         u8              head;           /* Insertion index in buffer[] */
 183         u8              tail;           /* Removal index in buffer[] */
 184         u8              need_free;      /* Mask of kfree'able items in buffer[] */
 185         struct module   *owner;         /* Owner module for strings that don't then need freeing */
 186         char            *buffer[8];
 187 };
 188
 189 extern __attribute__((format(printf, 4, 5)))
 190 void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...);
 191
 192 #define __logfc(fc, l, fmt, ...) logfc((fc)->log.log, NULL, \
 193                                         l, fmt, ## __VA_ARGS__)
 194 #define __plog(p, l, fmt, ...) logfc((p)->log, (p)->prefix, \
 195                                         l, fmt, ## __VA_ARGS__)
 196 /**
 197  * infof - Store supplementary informational message
 198  * @fc: The context in which to log the informational message
 199  * @fmt: The format string
 200  *
 201  * Store the supplementary informational message for the process if the process
 202  * has enabled the facility.
 203  */
 204 #define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__)
 205 #define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__)
 206 #define infofc(p, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__)
 207
 208 /**
 209  * warnf - Store supplementary warning message
 210  * @fc: The context in which to log the error message
 211  * @fmt: The format string
 212  *
 213  * Store the supplementary warning message for the process if the process has
 214  * enabled the facility.
 215  */
 216 #define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__)
 217 #define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__)
 218 #define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__)
 219
 220 /**
 221  * errorf - Store supplementary error message
 222  * @fc: The context in which to log the error message
 223  * @fmt: The format string
 224  *
 225  * Store the supplementary error message for the process if the process has
 226  * enabled the facility.
 227  */
 228 #define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__)
 229 #define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__)
 230 #define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS__)
 231
 232 /**
 233  * invalf - Store supplementary invalid argument error message
 234  * @fc: The context in which to log the error message
 235  * @fmt: The format string
 236  *
 237  * Store the supplementary error message for the process if the process has
 238  * enabled the facility and return -EINVAL.
 239  */
 240 #define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL)
 241 #define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINVAL)
 242 #define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL)
 243
 244 #endif /* _LINUX_FS_CONTEXT_H */